A control method for long-term balanced output power of two independent power supply devices

Abstract

This invention discloses a long-term balanced control method for the output of two independent power supply devices. The method controls these two independent power supply devices, each drawing power from the center tap of a battery pack. The first power supply draws power from the first terminal (e.g., positive terminal) and the midpoint of the battery pack, while the second power supply draws power from the midpoint and the second terminal (e.g., negative terminal). At least the first power supply device is controlled according to the following method. This balancing scheme ensures long-term balanced output power from the two DC power supply devices, extending the battery pack's lifespan without requiring additional hardware. It is also applicable to other applications requiring long-term balanced power output. After three months of operation, the voltage difference between the two power supplies controlled by this method is only about 10V, which helps extend the battery pack's lifespan, and the output power of the two power supply devices remains balanced over a long period.

Description

Technical Field

[0001] This invention relates to the field of uninterruptible power supplies, and more specifically to a control method for long-term balanced output power of two independent power supply devices. Background Technology

[0002] DC power grids are a crucial component of shipboard electrical systems, and DC power supply units are the power supply equipment for these grids, providing highly reliable and high-quality electrical energy to various loads on the ship. To ensure the reliability of power supply to critical loads, some DC power supply units will use battery banks as input to ensure reliable power supply even if the generator system fails. However, the voltage of the battery bank may differ significantly from the voltage required by the load; that is, the input voltage and output voltage of the DC power supply unit will differ considerably. This will lead to design difficulties for the DC power supply unit and poor stability under light loads. Therefore, the input voltage of the DC power supply unit will be drawn from the center tap of the battery bank, such as... Figure 1 As shown, two DC power supplies draw power from the upper and lower halves of the battery pack, respectively. Due to the inconsistent output characteristics of the two DC power supplies, the output power is unbalanced. After prolonged operation, the voltage between the upper and lower halves of the battery pack will become unbalanced, severely impacting the battery pack's lifespan. Therefore, it is necessary to implement balanced control of the output power of the two DC power supplies.

[0003] Traditional methods for balancing output power involve adding switches, switching control devices, and energy meters to the input of the DC power supply unit. When the voltage of half of the battery is lower than that of the other half, the input switch of the lower-voltage branch power supply unit is automatically disconnected, allowing the higher-voltage branch power supply unit to provide all the power to the load. However, this method requires additional hardware and advance design and planning, making it difficult to implement in existing shipboard power systems and equipment.

[0004] In addition, current conventional methods for balancing the output power of DC power supplies include average current sharing and external current sharing controllers. However, these methods require dedicated monitoring modules and are suitable for current sharing across multiple power modules within a single power supply. For two independent DC power supply units, the commonly used current sharing method is droop current sharing. This method performs well during short-term operation of the DC power supply unit, but its effectiveness deteriorates after long-term operation, such as after 2-3 months, requiring readjustment of the droop coefficient, making it unsuitable for practical engineering applications. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a control method for long-term balanced output power of two independent power supply devices. This method is applicable to two DC power supply devices drawing power from the center tap of a battery bank in a DC power grid. It enables long-term balanced output power between the two DC power supply devices, extending the lifespan of the battery bank without requiring additional hardware. It can also be applied to other applications requiring long-term balanced output power from power supply devices.

[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 provided for controlling the dual independent power supply device, wherein the dual independent power supplies draw power from the center tap of a battery pack, the first power supply device draws power from the first terminal and the midpoint of the battery pack, and the second power supply device draws power from the midpoint and the second terminal of the battery pack, wherein at least the first power supply device is controlled according to the following method, the method comprising 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, reaching the first threshold ΔU in1 The above is based on step size ΔU c The command U to gradually decrease the output voltage of the first power supply unit c Each adjustment step has a set delay time between each step to ensure the output voltage command U is maintained. c It changes slowly; set Flag = 4 and set the lower limit U of the output voltage command. cl1 Limit the output voltage command when U c cl1 At that time, let U c =U cl1 Output voltage error value err=U c -U o The output voltage error value err is fed back to the PI control loop of the first power supply unit to control the first power supply unit.

[0009] 2) If the input voltage of the second power supply is less than the input voltage of the first power supply, reaching the first threshold ΔU in1 The above is based on step size ΔU c The command U to gradually increase the output voltage of the first power supply unit c Each adjustment step has a set delay time between each step to ensure the output voltage command U is maintained. c It changes slowly; let 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 At that time, let U c =U​cl2 Output voltage error value err=U c -U o The output voltage error value err is fed back to the PI control loop of the first power supply unit to control the first power supply unit.

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

[0011] 4) When the input voltage difference between the second power supply unit and the first power supply unit is within ΔU in2 ~ΔU in1 or -ΔU in2 ~-ΔU in1 Between, and when Flag=2, the output voltage error value err=U c -U o -U Id Among them, the output voltage command U c No adjustment is made; the error adjustment coefficient U Id =I d / 128, the output voltage error value err is fed back to the PI control loop of the first power supply unit to control the first power supply unit, where I d This 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 the value is between 2 and Flag is not equal to 2, the output voltage error value err = U c -U o Among them, the output voltage command U c Without making any adjustments, the output voltage error value err is fed back to the PI control loop of the first power supply unit to control the first power supply unit.

[0013] Preferably, the first threshold ΔU in1=0.1*(Behicle pack maximum voltage - Battery pack minimum voltage).

[0014] The second threshold ΔU in2 =0.075*(Behicle pack maximum voltage - Battery pack minimum voltage).

[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] Adjusting step size ΔU c =0.0016 * rated output voltage.

[0018] The highest voltage of the battery pack refers to the voltage of the battery section supplying power to a single power source after it is fully charged (600V in the embodiment); the lowest voltage of the battery pack refers to the voltage of the battery section supplying power to a single power source after it is fully discharged (400V in the embodiment).

[0019] It should be noted that the invention combines PI control. For one power supply device, traditional voltage PI control can be used, while for the other power supply device, the control method of this invention is used to generate an error signal and feed it back to the PI loop for feedback control.

[0020] Technical effect

[0021] The balancing scheme of this invention ensures long-term balanced power output from two DC power supply units, extending the battery pack's lifespan without requiring additional hardware. It is also applicable to other applications requiring long-term balanced power output from power supply units.

[0022] Field test results show that when using traditional PI control or droop control methods, the initial voltage of the upper half of the battery bank is approximately DC580V, and the voltage of the lower half is approximately DC574V. After about 3 months of operation, the voltage of the upper half of the battery bank is approximately DC492V, and the voltage of the lower half is approximately DC417V, showing a large voltage difference that seriously affects the service life of the battery bank. When using the method proposed in this invention, the initial voltage of the upper half of the battery bank is approximately DC585V, and the voltage of the lower half is approximately DC578V. After about 3 months of operation, the voltage of the upper half of the battery bank is approximately DC453V, and the voltage of the lower half is approximately DC443V, showing a smaller voltage difference. This is beneficial for extending the service life of the battery bank, and the output power of the two power supply units can remain balanced over a long period. Attached Figure Description

[0023] Figure 1This is a schematic diagram of the power supply of two DC power supply devices that draw power from the center tap of the battery pack according to the present invention.

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

[0025] Figure 3 This invention provides a long-term output power balance control algorithm. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0027] This invention proposes a control method for long-term balanced output power of two independent power supply devices, the control method being as follows: Figure 2 As shown, the control algorithm flowchart is as follows: Figure 3 As shown.

[0028] The following explanation uses a DC 25V power supply as an example. The battery pack voltage is approximately DC 800-1200V. The DC power supply draws power from the center tap of the battery pack (the entire battery pack is divided into two parts, such as...). Figure 1 As shown in the figure, the input voltage is approximately DC400-600V, and the rated output voltage is DC25V.

[0029] Parameter description:

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

[0031] err: Output voltage error value;

[0032] U in1 The input voltage of the first DC power supply device is obtained through sampling.

[0033] U in2 The input voltage of the second DC power supply is obtained through sampling or communication.

[0034] ΔU in1 =20V: First threshold value for input voltage adjustment range;

[0035] ΔU in2 =15V: Second threshold of input voltage adjustment range;

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

[0037] U cl1 =24.8V: Lower limit for output voltage adjustment;

[0038] Ucl2 =26.8V: Upper limit of output voltage adjustment;

[0039] U o The actual output voltage of this device is obtained through sampling.

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

[0041] I d Load current, obtained through sampling;

[0042] Flag: Flag bit.

[0043] DC power supplies typically employ a PI control method for output voltage. This involves subtracting the commanded output voltage from the actual output voltage to obtain an output voltage error value (err). This error value is then regulated by the PI controller and modulated using PWM to generate a PWM wave, which controls the hardware circuit output. The method proposed in this invention will be used to generate the output voltage error value (err), thereby achieving long-term balanced control of the output power. This control method only needs to be applied to one DC power supply unit, while the other unit continues to use the traditional PI control method. The following description uses the first power supply unit as an example of applying this invention's control method:

[0044] 1) If the input voltage of the second power supply is greater than the input voltage of the first power supply by ΔU in1 = Above 20V, according to step size ΔU c =0.04V Gradually decrease the output voltage command U of the first power supply device c For each adjustment step, a certain time delay is set to ensure the output voltage command U is received. c The change is gradual to prevent power supply instability; therefore, Flag = 4. The lower limit value U of the output voltage command is also set. cl1 =24.8V, limiting the output voltage command, when U c cl1 At that time, let 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 is less than the input voltage of the first power supply by ΔU in1 = Above 20V, according to step size ΔU c =0.04V gradually increase the output voltage command U of the first power supply device c For each adjustment step, a certain time delay is set to ensure the output voltage command U is received. c ​The change is gradual to prevent power supply instability; therefore, Flag = 3. The upper limit value U of the output voltage command is also set. cl2 =26.8V, limiting the output voltage command, when U c >U cl2 At that time, let 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 unit and the first power supply unit is within ±ΔU in2 When the voltage is within ±15V, the output voltage error value err = U c -U o -U Id The output voltage command U c Without adjustment (which could be the initial value, or the value after adjustments based on cases 1) or 2), the error adjustment coefficient U... Id =I d / 128, and set Flag=2.

[0047] 4) When the input voltage difference between the second power supply unit and the input voltage of this unit is within ΔU in2 ~ΔU in1 or -ΔU in2 ~-ΔU in1 When the voltage is between 15V and 20V or between -15V and -20V, and Flag = 2, the output voltage error value err = U c -U o -U Id Among them, the output voltage command U c No adjustment is made (this could be the initial value, or the value after adjustments based on cases 1) or 2), and 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 When the voltage is between 15V and 20V or between -15V and -20V, and Flag is not equal to 2, the output voltage error value err = U c -U o Among them, the output voltage command U c No adjustment is made (this could be the initial value, or the value after adjustments based on cases 1) or 2).

[0049] In all 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 to the PI control loop for PI control.

[0050] Taking the power supply in this embodiment as an example, the field test results show that when using traditional PI control or droop control methods, the initial voltage of the upper half of the battery 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 is about DC492V and the voltage of the lower half is about DC417V. The voltage difference is large, around 70-80V, which seriously affects the service life of the battery pack.

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

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

[0053] In summary, this invention proposes a control method for long-term balanced output power of two independent power supply devices. This method is applicable to two DC power supply devices drawing power from the center tap of a battery bank in a ship's DC power grid. It enables long-term balanced output power between the two DC power supply devices, extending the lifespan of the battery bank without requiring additional hardware. It can also be applied to other applications requiring long-term balanced output power from power supply devices.

[0054] Although the principles of the present invention have been described in detail above with reference to preferred embodiments, those skilled in the art should understand that the above embodiments are merely illustrative explanations of the implementation of the present invention and are not intended to limit the scope of the present invention. The details in the embodiments do not constitute a limitation on the scope of the present invention. Any obvious changes, such as equivalent transformations or simple substitutions, based on the technical solutions 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 to control the dual independent power supply device, wherein the dual independent power supplies draw power from the center tap of a battery pack, the first power supply device draws power from the first terminal and the midpoint of the battery pack, and the second power supply device draws power from the midpoint and the second terminal of the battery pack, wherein... At least the first power supply device is controlled according to the following method, characterized in that the method includes the following steps: 1) Measure the input voltage of the first and second power supply units in real time. If the input voltage of the second power supply unit is greater than the input voltage of the first power supply unit, reaching the first threshold ΔU... in1 According to step size ΔU c The command U to gradually decrease the output voltage of the first power supply unit c For each adjustment step, a certain time delay is set to ensure the output voltage command U is received. c It changes slowly; set Flag = 4 and set the lower limit U of the output voltage command. cl1 Limit the output voltage command when U c cl1 At that time, let U c =U cl1 Output voltage error value err=U c -U o The output voltage error value err is fed back to the PI control loop of the first power supply unit to control the first power supply unit.​ 2) If the input voltage of the second power supply is less than the input voltage of the first power supply, reaching the first threshold ΔU in1 According to step size ΔU c The command U to gradually increase the output voltage of the first power supply unit c For each adjustment step, a certain time delay is set to ensure the output voltage command U is received. c It changes slowly; let 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 At that time, let U c =U cl2 Output voltage error value err=U c -U o The output voltage error value err is fed back to the PI control loop of the first power supply unit to control the first power supply unit. 3) When the input voltage of the second power supply device differs from the input voltage of the first power supply device by the second threshold ±ΔU in2 When the error is within a certain range, the output voltage error value err = U c -U o -U Id The output voltage command U c No adjustment is made; the error adjustment coefficient U Id =I d / 128, and set Flag=2, feed the output voltage error value err back to the PI control loop of the first power supply unit to control the first power supply unit, where I d This is the load current; 4) When the input voltage difference between the second power supply unit and the first power supply unit is within ΔU in2 ~ΔU in1 or -ΔU in2 ~-ΔU in1 Between, and when Flag=2, the output voltage error value err=U c -U o -U Id Among them, the output voltage command U c No adjustment is made; the error adjustment coefficient U Id =I d / 128, the output voltage error value err is fed back to the PI control loop of the first power supply unit to control the first power supply unit, where I d This is the load current; 5) When the input voltage difference between the second power supply unit and the first power supply unit is within ΔU in2 ~ΔU in1 or -ΔU in2 ~-ΔU in1 When the value is between 2 and Flag is not equal to 2, the output voltage error value err = U c -U o Among them, the output voltage command U c Without making any adjustments, the output voltage error value err is fed back to the PI control loop of the first power supply unit to control the first power supply unit.

2. The long-term equalization control method for the output of dual independent power supply devices according to claim 1, characterized in that, The first threshold ΔU in1 =0.1*(Behicle pack maximum voltage - Battery pack minimum voltage).

3. The long-term equalization control method for the output of dual independent power supply devices according to claim 1, characterized in that, The second threshold ΔU in2 =0.075*(Behicle pack maximum voltage - Battery pack minimum voltage).

4. The long-term equalization control method for the output of dual independent power supply devices 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 equalization control method for the output of dual independent power supply devices 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 equalization control method for the output of dual independent power supply devices according to claim 1, characterized in that, Adjusting step size ΔU c =0.0016 * rated output voltage.

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