Hydropower station direct-current power supply system for realizing open-circuit follow current function and construction method of hydropower station direct-current power supply system

Abstract

The invention discloses a hydropower station direct-current power supply system for realizing an open-circuit follow current function and a construction method thereof. The system comprises a DC / DC element, a diode and a storage battery, the method comprises the following steps: calculating the total number of storage batteries and the rated output power of a single storage battery; calculating the total number of DC / DC elements and the number of storage batteries connected with each DC / DC element; calculating the standard voltage, the maximum stable discharge current and the capacity of each storage battery; calculating capacitance and inductance in the DC / DC element; constructing a two-stage PID (Proportion Integration Differentiation) current loop controller with weight distribution in the DC / DC element; and according to the parameters, constructing a hydropower station direct-current power supply system for realizing an open-circuit follow current function. According to the invention, an open-circuit follow current function can be realized when a single storage battery fails, and the economical efficiency of the system can be improved; if the storage battery breaks down, the load rated voltage can be effectively stabilized, and the load power supply stability is improved; and if both the DCDC and the storage battery have faults, the output current between the DCDCs can be effectively distributed, so that the storage battery without faults is reasonably discharged, and the energy utilization efficiency of the system is improved.

Description

Technical Field

[0001] The invention relates to a direct current power supply system for a hydropower station for realizing an open-circuit freewheeling function and a construction method thereof, and belongs to the technical field of power electronics. Background Art

[0002] When the entire hydropower station loses power, in order to ensure the normal DC power supply of the load, it is necessary to rely on the hydropower station DC system for power supply. At present, hydropower stations mostly use lead-acid battery groups to form DC systems. Although the failure rate of lead-acid batteries is low, and the number of power outages in the entire hydropower station is small each year, lead-acid battery failures rarely occur. However, the simple use of lead-acid batteries in series and combined with transformers is prone to some problems. First, based on the series connection method of the battery, if a single battery fails, the entire battery group will not work properly. Secondly, it is difficult to achieve the load voltage regulation function using a transformer, resulting in poor load voltage stability. Finally, if the battery fails, the use of a backup battery group for power supply will increase the investment cost.

[0003] Therefore, in order to further improve the reliability, stability and economy of the DC system, prevent power outages caused by failure of a single battery, and improve the power supply quality of the battery pack, it is necessary to construct a lead-acid battery DC power supply system with open-circuit freewheeling function for hydropower stations. Summary of the invention

[0004] The present invention provides a method for constructing a direct current power supply system of a hydropower station for realizing an open circuit freewheeling function, so as to solve the problem that a single storage battery is damaged and the entire storage battery group cannot supply power, thereby ensuring the normal operation of the load.

[0005] The technical solution of the present invention is:

[0006] According to a first aspect of the present invention, a hydropower station DC power supply system for realizing an open circuit freewheeling function is provided, wherein the hydropower station DC power supply system for realizing an open circuit freewheeling function comprises a DC / DC element, a diode, and a battery; The batteries are connected in series, and a diode is connected in parallel to each battery to provide the blocking function of a single battery; each DC / DC element and Battery connection, A DC / DC element is connected in parallel with the load to achieve adjustable load voltage.

[0007] According to a second aspect of the present invention, there is provided a method for constructing a DC power supply system of a hydropower station for realizing an open circuit freewheeling function, comprising the following steps:

[0008] S1. Introduce the battery number correction coefficient to calculate the total number of batteries; determine the rated output power of a single battery based on the total number of batteries and the total power of the batteries;

[0009] S2. Calculate the total number of DC / DC components based on the total number of batteries and the rated output power of each battery; determine the number of batteries connected to each DC / DC component based on the number of DC / DC components;

[0010] S3. Calculate the standard voltage V of each battery cell , Maximum stable discharge current I cell and capacity Q cell ;

[0011] S4. Calculate the capacitance and inductance in the DC / DC components;

[0012] S5. Construct a two-stage PID current loop controller with weight distribution in the DC / DC element;

[0013] S6. Based on the parameters in S1-S4, construct a hydropower station DC power supply system for realizing an open-circuit freewheeling function as described in claim 1.

[0014] Furthermore, in S1, the total number of batteries and the rated output power of a single battery are expressed as follows:

[0015] P total =μ*P r

[0016]

[0017] Where P total represents the total power of the battery; μ represents the standby configuration rate, μ>1; P r is the rated power of the load; Represents the total number of batteries in the DC power supply system, round is the integer operation, ε LA_B_Achtual Indicates the actual failure rate of a single battery, b is the correction factor for the number of batteries; ε LA_B_Theory is the theoretical failure rate of each battery, k is the actual discharge times of the DC power supply system of the hydropower station in each year; P i Represents the rated output power of the ith battery.

[0018] Furthermore, in S2, the total number of DC / DC elements and the number of batteries connected to each DC / DC element are expressed as follows:

[0019]

[0020] In the formula, is the total number of DC / DC components; Indicates the number of connected storage batteries for each DC / DC component; Indicates the total number of storage batteries in the DC power supply system; P i Indicates the rated output power of the i-th storage battery; P r Is the rated power of the load; μ represents the standby configuration ratio, μ > 1.

[0021] Furthermore, the standard voltage V of each storage battery is calculated cell , the maximum stable discharge current I cell and the capacity Q cell , and the expression is:

[0022]

[0023]

[0024] Q cell = I cell * C cell

[0025] In the formula, D is the duty cycle of the DC / DC component, 0 < D < 1; V load is the rated voltage of the load; C cell is the discharge rate of the storage battery; P i Indicates the rated output power of the i-th storage battery; Indicates the number of connected storage batteries for each DC / DC component.

[0026] Furthermore, the capacitance and inductance in the DC / DC component are calculated, and the expression is:

[0027]

[0028] 50mV < ΔV < 200mV

[0029] 20kHz < f sw < 100kHz

[0030] In the formula, C DCDC is the capacitance of the DC / DC component; I load represents the load current; D is the duty cycle of the DC / DC component, 0 < D < 1; ΔV represents the DC / DC output ripple voltage, f sw represents the DC / DC switching frequency; L DCDC is the inductance of the DC / DC component, Z Load is the load impedance value; I load represents the load current.

[0031] Furthermore, a two-stage PID current loop controller with weight distribution is constructed in the DC / DC component, and the model is as follows:

[0032]

[0033] In the formula, is the time-series output of the ith DC / DC element of the first-level PID control, is the timing input quantity of the ith DC / DC element of the first-level PID control, is the proportional gain of the ith DC / DC element of the first-level PID control, is the integral gain of the ith DC / DC element of the first-level PID control, is the differential gain of the i-th DC / DC element of the first-level PID control; is the sequential output of the ith DC / DC element of the second-level PID control, is the timing input quantity of the ith DC / DC element of the second-level PID control, is the proportional gain of the ith DC / DC element of the second-level PID control, is the integral gain of the ith DC / DC element of the second-level PID control, is the differential gain of the ith DC / DC element of the second-level PID control; V load is the load rated voltage, is the output timing voltage of the i-th DC / DC element; is the reference timing current of the ith DC / DC element, is the input timing current of the i-th DC / DC element; is the input timing voltage of the i-th DC / DC element, is the input timing voltage and of all DC / DC components; is the output timing current of the i-th DC / DC element; is the total number of DC / DC components.

[0034] According to a third aspect of the present invention, a processor is provided, the processor being used to execute an operation, the operation comprising executing any one of the above-mentioned methods for constructing a direct current power supply system for a hydropower station for realizing an open-circuit freewheeling function.

[0035] The beneficial effects of the present invention are as follows: the present invention is based on basic electrical components such as batteries, diodes, DC / DC elements (DC boost components), etc., and realizes fault blocking of a single battery in a loop composed of a single DC / DC and a battery, realizes open-circuit continuous flow of a single battery, and improves the economy of the DC system; at the same time, a current loop PID controller with weight distribution is designed to adjust the DC / DC duty cycle, so that when a single or multiple batteries fail, the output currents between the DC / DCs are balanced, the output power of each battery is reasonably distributed, the utilization efficiency of the entire DC system is improved, and finally the stability of the load voltage and power is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flowchart of the construction method of the present invention;

[0037] Figure 2 It is a schematic diagram of the construction of batteries, diodes, and DC / DC components;

[0038] Figure 3 This is a schematic diagram of the connection between DC / DC and load;

[0039] Figure 4 It is a simulation result diagram provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other arbitrarily without conflict.

[0041] refer to Figure 1-3 As shown, according to a first aspect of an embodiment of the present invention, a hydropower station DC power supply system for realizing an open circuit freewheeling function is provided, wherein the hydropower station DC power supply system for realizing an open circuit freewheeling function comprises a DC / DC element, a diode, and a battery; The batteries are connected in series, and a diode is connected in parallel to each battery to provide the blocking function of a single battery; each DC / DC element is connected to Battery connection, A DC / DC element is connected in parallel with the load to achieve adjustable load voltage.

[0042] Exemplarily, the battery is a lead-acid battery.

[0043] refer to Figure 1-Figure 4According to a second aspect of an embodiment of the present invention, there is provided a method for constructing a DC power supply system of a hydropower station for realizing an open circuit freewheeling function, comprising the following steps:

[0044] S1. Calculate the total number of batteries and the rated output power of each battery:

[0045] P total =μ*P r (1)

[0046]

[0047] Formula 1 indicates that the total power of the configured battery must be greater than the power required by the rated load, where P total represents the total power of the battery; μ represents the backup configuration rate (determined by the investment of the hydropower station in the DC system, the larger the μ, the higher the reliability), μ>1; P r is the rated power of the load. Formula 2 is the calculation formula for the number of batteries to be configured. Indicates the number of lead-acid batteries in the DC power supply system, round is the integer operation, ε LA_B_Actual represents the actual failure rate of a single lead-acid battery, b is the battery number correction coefficient, b∈{0,1,2,3…n} a natural number; Formula 3 represents the calculation formula for the actual failure rate of each lead-acid battery, ε LA_B_Theory is the theoretical failure rate of each lead-acid battery (provided by the manufacturer, assuming that the lead-acid batteries used in the hydropower station are of the same model and provided by the same manufacturer, and the theoretical failure rates are the same), k is the actual number of discharges of the DC power supply system of the hydropower station in each year. Formula 4 represents the power of each battery (assuming that the power of each lead-acid battery in the DC system of the hydropower station is the same), P i Represents the power of the i-th lead-acid battery.

[0048] S2. Calculate the number of DC / DC components

[0049]

[0050] Formula 5 shows the formula for determining the number of DC / DC components to be configured. is the total number of DC / DC components; in formula 6, Indicates the number of batteries connected to each DC / DC unit.

[0051] S3. Calculate the standard voltage V of each lead-acid battery cell , Maximum stable discharge current I cell and capacity Q cell :

[0052]

[0053] Q cell = I cell * C cell (9)

[0054] Equation 7 represents the determination formula for the standard voltage quantity of each lead-acid battery. D is the duty cycle of the DC / DC component, 0 < D < 1, and V load is the rated voltage of the load; Equation 8 represents the determination formula for the maximum stable discharge current of each lead-acid battery. Equation 9 represents the determination formula for the capacity of each lead-acid battery, where C cell is the battery discharge rate, that is, when discharging at the maximum stable current I cell it can be discharged for C cell hours.

[0055] S4. Calculate the capacitance and inductance in the DC / DC component:

[0056]

[0057] 50 mV < ΔV < 200 mV (13)

[0058] 20 kHz < f sw < 100 kHz (14)

[0059] Equation 10 represents the calculation formula for the capacitance in the DC / DC component. C DCDC is the capacitance of the DC / DC component (unit: F), I load represents the load current (unit: A), D is the duty cycle of the DC / DC component, 0 < D < 1, ΔV represents the DC / DC output ripple voltage (unit: V), and f sw represents the DC / DC switching frequency (unit: Hz); Equation 11 represents the value range of the inductance L DCDC of the DC / DC component (unit: H), Z Load is the load impedance value; Equation 12 represents the calculation formula for the load current I load ; Equation 13 represents the value range of the output ripple voltage ΔV; Equation 14 represents the value range of the DC / DC switching frequency f sw value range.

[0060] S5. Construct a two-stage PID current loop controller with weight distribution in the DC / DC component, and the control algorithm is as follows:

[0061]

[0062]

[0063] Equation 15 represents the output calculation formula of the first-stage PID control, where is the time-series output of the ith DC / DC element of the first-level PID control, is the timing input quantity of the ith DC / DC element of the first-level PID control, is the proportional gain of the ith DC / DC element of the first-level PID control, is the integral gain of the ith DC / DC element of the first-level PID control, is the differential gain of the ith DC / DC element of the first-level PID control; Formula 16 represents the output calculation formula of the second-level PID control, where is the sequential output of the ith DC / DC element of the second-level PID control, is the timing input quantity of the ith DC / DC element of the second-level PID control, is the proportional gain of the ith DC / DC element of the second-level PID control, is the integral gain of the ith DC / DC element of the second-level PID control, is the differential gain of the ith DC / DC element of the second-level PID control; Formula 17 represents the input calculation formula of the first-level PID control, where V load is the rated voltage of the load, is the output timing voltage of the i-th DC / DC element; Formula 18 represents the input calculation formula of the second-level PID control, where is the reference timing current of the ith DC / DC element, is the input timing current of the i-th DC / DC element; Formula 19 represents the reference timing current calculation formula, where is the input timing voltage of the i-th DC / DC element, is the input timing voltage and of all DC / DC components, is the output timing current of the i-th DC / DC element; Formula 20 is the calculation formula for the input timing voltage and of all DC / DC elements. In the above Formulas 15 to 20, It is a real measurement that changes with time (it can be measured in real time by a device that measures current or voltage). V load is a known variable, and the remaining variables are time series calculation quantities.

[0064] S6. Based on the above-mentioned component parameters, a DC power supply system for a hydropower station is constructed to realize an open-circuit freewheeling function.

[0065] S6.1. Each lead-acid battery is connected in parallel with a diode, and each DC / DC element is connected in parallel with a diode. Lead-acid batteries connected, The lead-acid batteries are connected in series. Figure 2 shown.

[0066] S6.2, A DC / DC is connected in parallel with the load, and the construction diagram is as follows Figure 3 shown.

[0067] The following is an explanation based on specific cases:

[0068] Assuming that the rated power of a DC system load of a micro hydropower station is 580W and the rated voltage of the load is 220V, a DC power supply system for a hydropower station is designed to realize the open-circuit freewheeling function. The system is required to be reliable, stable in load power supply, and economical.

[0069] Step 1. Based on the above assumptions, the known condition is P r =580W, V load =220V,ε LA_B_Theory =3% (provided by the manufacturer), μ = 1.5 (power station design requirements), k = 105 (fill in according to the actual situation of the power station), D (DC / DC duty cycle) = 0.865 (initial setting value), ΔV = 100mV, f sw =50kHz, C cell =5 (industry standard is between 3-5), (The present invention does not discuss the selection of PID parameters for the time being).

[0070] Step 2: When the battery number correction coefficient is 0, the number of lead-acid batteries is 39 and the power of each lead-acid battery is 22.3W.

[0071] Step 3. The total number of DC / DCs obtained by implementing step S2 is taken as an integer of 3, and the number of batteries connected to each DC / DC element is taken as an integer of 13, that is, each DC / DC is connected to 13 batteries.

[0072] Step 4: Calculate V by implementing step S3 cell =2.28V, I cell =0.1014A, Q cell =0.5Ah.

[0073] Step 5. Calculate C by implementing step S4 DCDC =1.5*10 -4 (F), L DCDC Take 0.0025H.

[0074] Step 6. Design a PID current loop controller by implementing step S5.

[0075] Step 7: Establish a simulation model based on Matlab by implementing step S6.

[0076] The above matlab simulation model is used to describe and analyze the simulation effect diagram under the condition that there are three DC / DC converters, PID adjustment duty cycle, and one battery in the battery pack corresponding to the three DC / DCs fails at 0.5 seconds, such as Figure 4 The dynamic changes of the input current and output current of the three DC / DCs under battery failure conditions show that the DC / DC reasonably maintains the system power balance when adding the weighted PID control mode. When the PID is used for power distribution, the DC / DC duty cycle is adjusted when the battery is damaged, thereby ensuring the stability of the load rated working voltage and the rationality of the battery output current.

[0077] By applying the above technical solution, it can be known that the present invention can realize the open circuit freewheeling function when a single battery fails, which can improve the economy of the system; secondly, if a battery fails, the rated voltage of the load can be effectively stabilized, thereby improving the stability of the load power supply. At the same time, if both the DCDC and the battery fail, the system can effectively distribute the output current between each DCDC, so that the battery that has not failed can be discharged reasonably, thereby improving the energy utilization efficiency of the system.

[0078] According to a third aspect of an embodiment of the present invention, a processor is provided, wherein the processor is used to execute an operation, wherein the operation includes executing any one of the above-mentioned methods for constructing a direct current power supply system for a hydropower station for realizing an open-circuit freewheeling function.

[0079] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A DC power supply system for a hydropower station for realizing an open circuit freewheeling function, characterized in that: The hydropower station DC power supply system for realizing the open circuit freewheeling function comprises a DC / DC element, a diode, and a battery; The batteries are connected in series, and a diode is connected in parallel to each battery to provide the blocking function of a single battery; each DC / DC element and Battery connection, A DC / DC element is connected in parallel with the load to achieve adjustable load voltage.

2. A method for constructing a DC power supply system for a hydropower station for realizing an open circuit freewheeling function, characterized in that: The following steps are involved: S1. Introduce the battery number correction coefficient to calculate the total number of batteries; determine the rated output power of a single battery based on the total number of batteries and the total power of the batteries; S2. Calculate the total number of DC / DC components based on the total number of batteries and the rated output power of each battery; determine the number of batteries connected to each DC / DC component based on the number of DC / DC components; S3. Calculate the standard voltage V of each battery cell , Maximum stable discharge current I cell and capacity Q cell ; S4. Calculate the capacitance and inductance in the DC / DC components; S5. Construct a two-stage PID current loop controller with weight distribution in the DC / DC element; S6. Based on the parameters in S1-S4, construct a hydropower station DC power supply system for realizing an open-circuit freewheeling function as described in claim 1.

3. The method for constructing a DC power supply system for a hydropower station for realizing an open circuit freewheeling function according to claim 1, characterized in that: In S1, the total number of batteries and the rated output power of a single battery are expressed as follows: P total =μ*P r Where P total represents the total power of the battery; μ represents the standby configuration rate, μ>1; P r is the rated power of the load; Represents the total number of batteries in the DC power supply system, round is the integer operation, ε LA_B_Actual Indicates the actual failure rate of a single battery, b is the correction factor for the number of batteries; ε LA_B_Theory is the theoretical failure rate of each battery, k is the actual discharge times of the DC power supply system of the hydropower station in each year; P i Represents the rated output power of the ith battery.

4. The method for constructing a hydropower station DC power supply system for realizing an open circuit freewheeling function according to claim 1, characterized in that: In S2, the total number of DC / DC elements and the number of batteries connected to each DC / DC element are expressed as follows: In the formula, is the total number of DC / DC components; Indicates the number of batteries connected to each DC / DC element; Indicates the total number of batteries in the DC power supply system; P i represents the rated output power of the ith battery; P r is the rated power of the load; μ represents the standby configuration rate, μ>1.

5. The method for constructing a hydropower station DC power supply system for realizing an open circuit freewheeling function according to claim 1, characterized in that: The calculation of the standard voltage V of each battery cell , Maximum stable discharge current I cell and capacity Q cell , the expression is: Q cell =I cell *C cell Where D is the duty cycle of the DC / DC element, 0 <D<1;V load is the rated voltage of the load; C cell is the battery discharge rate; P i represents the rated output power of the ith battery; Indicates the number of batteries connected to each DC / DC unit.

6. The method for constructing a hydropower station DC power supply system for realizing an open circuit freewheeling function according to claim 1, characterized in that: The calculation of capacitance and inductance in the DC / DC component is as follows: 50mV<ΔV<200mV 20kHz<f sw <100kHz Where, C DCDC is the capacitance of the DC / DC component; I load represents the load current; D is the duty cycle of the DC / DC component, 0 < D < 1; ΔV represents the DC / DC output ripple voltage, f sw represents the DC / DC switching frequency; L DCDC is the inductance of the DC / DC component, Z Load is the load impedance value; I load represents the load current.

7. The method for constructing a DC power supply system for a hydropower station for realizing an open circuit freewheeling function according to claim 1, characterized in that: The two-stage PID current loop controller with weight distribution is constructed in the DC / DC element, and the model is as follows: In the formula, is the time-series output of the ith DC / DC element of the first-level PID control, is the timing input quantity of the ith DC / DC element of the first-level PID control, is the proportional gain of the ith DC / DC element of the first-level PID control, is the integral gain of the ith DC / DC element of the first-level PID control, is the differential gain of the i-th DC / DC element of the first-level PID control; is the sequential output of the ith DC / DC element of the second-level PID control, is the timing input quantity of the ith DC / DC element of the second-level PID control, is the proportional gain of the ith DC / DC element of the second-level PID control, is the integral gain of the ith DC / DC element of the second-level PID control, is the differential gain of the ith DC / DC element of the second-level PID control; V load is the rated voltage of the load, is the output timing voltage of the i-th DC / DC element; is the reference timing current of the ith DC / DC element, is the input timing current of the i-th DC / DC element; is the input timing voltage of the i-th DC / DC element, is the input timing voltage and of all DC / DC components; is the output timing current of the i-th DC / DC element; is the total number of DC / DC components.

8. A processor, characterized in that: The processor is used to execute operations, and the operations include executing the method for constructing a hydropower station DC power supply system for realizing an open-circuit freewheeling function as described in any one of claims 2-7.

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