CN110957720B - Power supply system and method for stable power supply - Google Patents
Power supply system and method for stable power supply Download PDFInfo
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- CN110957720B CN110957720B CN201911120608.7A CN201911120608A CN110957720B CN 110957720 B CN110957720 B CN 110957720B CN 201911120608 A CN201911120608 A CN 201911120608A CN 110957720 B CN110957720 B CN 110957720B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
Abstract
The invention discloses a power supply system and a method for stably supplying power. In order to overcome the defect that in the prior art, power supply is required to be kept all the time when a bus fails; the invention adopts a generator set, an alternating current power grid, a load, a voltage sensor, a frequency detector, a compensation power supply, a frequency converter, a control switch and a standby power supply connected with the alternating current power grid, wherein the generator set generates power for the alternating current power grid, the alternating current power grid outputs the power to the load, and the load comprises a lower-level power distribution network and field equipment; the compensation power supply is connected with an alternating current power grid through a control switch, and the control switch receives the detected voltage and controls the compensation power supply to supply power or charge; and the frequency converter receives the detected frequency and controls the power generation frequency of the generator set. The power supply system not only ensures one kind of power supply, improves the continuous stability of power supply, but also ensures the stability of voltage and frequency of power supply, and improves the power supply quality.
Description
Technical Field
The invention relates to the technical field of power supply, in particular to a power supply system and a power supply method for stable power supply.
Background
Electric energy plays an important role in our life and production, is widely applied to various fields including power, traffic, illumination and textile, and promotes the development of science and technology and the development of the people economy. The stable power supply of the power grid affects the life and production of people, so people have urgent need for the stable power supply of the power grid. The problem of low voltage often still exists in the peak period of power consumption of the existing power grid power supply, which causes influence on life and production of users; the frequency of the power output by the power grid also influences the quality of the power consumption; when the bus fails, the power supply is required to be kept constantly, and the bus can be maintained without power failure.
In order to improve the stability of the power supply, there are many improvements to the power supply system. For example, a "power supply system and power supply method" disclosed in chinese patent literature, whose publication number "CN 110148955 a" includes: the system comprises an alternating current power grid, a controller, a storage battery and a bidirectional converter; the working principle of the power supply system is as follows: the controller is used for controlling the bidirectional converter to invert the direct current of the storage battery into alternating current to output electric energy to the alternating current power grid when the voltage of the alternating current power grid is lower than a preset voltage and the capacity of the storage battery is larger than a first preset capacity; the controller is also used for controlling the bidirectional converter to rectify the alternating current of the alternating current power grid into direct current to charge the storage battery when the voltage of the alternating current power grid is determined to be greater than the rated voltage and the capacity of the storage battery is determined to be less than a second preset capacity; wherein the first preset capacity is smaller than the second preset capacity. The system only stabilizes the voltage of the power supply system, but does not solve the problem that the power supply system needs to be kept in a power supply state all the time when the frequency of output power of the power supply system changes and a bus fails.
Disclosure of Invention
The invention mainly solves the problem that the prior art can not always maintain power supply when the bus fails; and the stability of the supply voltage is difficult to ensure during the peak time of electricity consumption; the power supply system for stably supplying power can provide a power supply when a bus fails, always keep the power supply of a power grid, and also keep the stability of output voltage and frequency during power utilization peak so as to ensure the quality of output power.
The technical problem of the invention is mainly solved by the following technical scheme:
the invention relates to a power supply system for stable power supply, which comprises a generator set, an alternating current power grid, a load and a standby power supply connected with the alternating current power grid, wherein the alternating current power grid outputs electricity to the load, and the load comprises a lower-level distribution network and field equipment; characterized in that the power supply system also comprises
A voltage sensor for detecting a voltage output by the AC power grid;
the frequency detector is used for detecting the frequency output by the alternating current power grid when the voltage output by the alternating current power grid is smaller than a rated voltage threshold;
the compensation power supply is connected with an alternating current power grid;
the control switch receives the detected voltage, and controls the compensation power supply to charge when the output voltage of the alternating current power grid is greater than a rated voltage threshold and the electric quantity of the compensation power supply is less than a first electric quantity threshold; when the output voltage of the alternating current power grid is smaller than the rated voltage threshold value, the output frequency is within the rated frequency threshold value, and the electric quantity of the compensation power supply is larger than the second electric quantity threshold value, or when the electric quantity of the compensation power supply is smaller than the second electric quantity threshold value, the compensation power supply is controlled to be charged;
and the frequency converter receives the detected frequency and controls the power generation frequency of the generator set.
Voltage sensors to detect voltage, frequency monitors to detect frequency, and frequency converters to control generator frequency are all well known devices. Under normal conditions, the generator set generates electricity, and the alternating current power grid transmits the electric energy to a load. When the alternating current power grid or the generator set breaks down and needs to be powered off, the standby power supply replaces the alternating current power grid to supply power to the load, and time is provided for maintenance. When the detected output voltage is lower than the rated voltage, the power supply frequency is within the rated frequency threshold value, and the electric quantity of the compensation power supply is greater than the first electric quantity threshold value, the control switch controls the compensation power supply to supply power to the load until the detected output voltage reaches the rated voltage; the first power threshold compensates for 90% of the power supply. When the detected frequency is not at the rated frequency threshold value, the frequency converter controls the power generation frequency of the generator set, so that the frequency reaches a stable rated value, and the motor is synchronously balanced. And when the output voltage of the alternating current power grid is smaller than the rated voltage threshold, the output frequency is within the rated frequency threshold, and the electric quantity of the compensation power supply is larger than the second electric quantity threshold, or when the electric quantity of the compensation power supply is smaller than the second electric quantity threshold, controlling the compensation power supply to charge. The second electric quantity threshold value is 25% of the electric quantity of the compensation power supply, and the compensation power supply is guaranteed to have enough electric quantity to supply power to the system when in use. The system can guarantee continuous power supply, so that electric energy is always continuous, the quality of output electric energy is guaranteed, the voltage and the frequency reach rated values, and the balance value of active power and reactive power is achieved. The power supply system is stable in power supply and stable in power supply quality.
Preferably, the compensation power supply comprises a rectifying circuit, an inverter circuit and a battery pack with a coulometer; the rectification circuit is a full-bridge rectification circuit formed by four thyristors, and the inverter circuit is a full-bridge inverter circuit formed by four thyristors; the input end of the rectifying circuit is connected with an alternating current power grid, and the output end of the rectifying circuit is connected with the battery pack; the input end of the inverter circuit is connected with the battery pack, and the output end of the inverter circuit is connected with the alternating current power grid. The rectification circuit changes alternating current into direct current to charge the battery pack, the inverter circuit converts the direct current in the battery pack into the alternating current, and when the voltage in the alternating current power grid is insufficient, the voltage of the alternating current power grid is increased. The battery pack charge amount detection device can monitor the electric quantity of the battery pack and is used for judging whether the battery is charged or discharged. The compensation power supply capable of charging and discharging is adopted, so that the voltage output by the power grid is stable and is greater than the rated voltage, and the power consumption of a user is ensured.
Preferably, the control switch is a single-pole three-position switch; the first contact is arranged between the alternating current power grid and the input end of the rectifying circuit, the second contact is suspended, and the third contact is arranged between the alternating current power grid and the output end of the inverter circuit; the first contact and the third contact are electromagnetic contacts. The control switch judges whether the compensation power supply is in a charging mode, a discharging mode or a standby mode according to the received voltage comparison signal and the electric quantity comparison signal, the state of the compensation power supply can be automatically controlled according to the electric quantity of the compensation power supply and the output voltage, the compensation power supply is guaranteed to have enough electric quantity as the compensation voltage of the alternating current power grid, the stability of the output voltage is further guaranteed, and the output voltage is not lower than the rated voltage.
Preferably, the control switch comprises a logic control circuit, and the logic control circuit comprises a first electric quantity comparator, a second electric quantity comparator, a voltage comparator, an and gate U1, an and gate U2, an not gate U3 and an not gate U4; the positive input end of the voltage comparator is rated voltage, the negative input end of the voltage comparator is connected with the voltage sensor, the output end of the voltage comparator is connected with the input end of the NOT gate U3, the output end of the NOT gate U3 is connected with one input end of the AND gate U1, and the output end of the voltage comparator is connected with one input end of the AND gate U2; the positive input end of the first electricity quantity comparator is a first electricity quantity threshold, the negative input end of the first electricity quantity comparator is connected with the output end of the electricity meter, the output end of the first electricity quantity comparator is connected with the other input end of the AND gate U1, and the output end of the AND gate U1 is connected with a first contact of the control switch; the positive input end of the second electric quantity comparator is a second electric quantity threshold, the negative input end of the second electric quantity comparator is connected with the output end of the electric quantity meter, the output end of the second electric quantity comparator is connected with the first contact of the control switch, the output end of the second electric quantity comparator is connected with the input end of the NOT gate U4, the output end of the NOT gate U4 is connected with the other input end of the AND gate U2, and the output end of the AND gate U2 is connected with the third contact of the control switch. The voltage sensor detects the output voltage, transmits the output voltage to a standard signal and enters the input end of the voltage comparator. The first electric quantity threshold value is 90% of the total electric quantity of the compensation power supply, and the second electric quantity threshold value is 25% of the total electric quantity of the compensation power supply. The compensation power supply is ensured to have enough electric quantity to be the compensation voltage of the alternating current power grid, power is not supplied when the electric quantity is insufficient, the output of the alternating current power grid is ensured not to be interfered, and the output of the alternating current power grid is ensured to be a stable value.
Preferably, the alternating current power grid comprises a first bus and a second bus, the first bus and the second bus are connected through a tie switch, and the first bus and the second bus are connected with different loads; the standby power supply is a diesel generator, and the output end of the diesel generator is respectively connected with the first bus and the second bus. The first bus and the second bus share different loads, so that the respective pressure of the two buses is reduced, enough margin can drive more loads, and the safety and stability of a power grid are ensured; the interconnection switch is normally disconnected, when one bus fails and needs to be maintained, the interconnection switch is closed, the other bus supplies power to the two paths of loads, the loads are guaranteed to be temporarily not powered off, and time is provided for adding a standby power supply and maintaining the fault bus; the diesel generator is used for generating power, the power supply power is large enough, the pressure of the power supply bus is reduced when one bus fails, and the normal power supply of a power grid is ensured when two buses fail, so that the time is provided for the maintenance of the buses. And uninterrupted power supply of the power grid is ensured.
Preferably, the alternating current power grid comprises a first bus and a second bus, the first bus and the second bus are connected through a tie switch, and the first bus and the second bus are connected with different loads; the standby power supply is a third bus, the third bus is respectively connected with the first bus and the second bus through a tie switch, and the third bus is in hot standby. Compare in diesel generator, the benefit of using the third bus is that the time of access is short, and hot standby is always, only need just can be for the electric wire netting power supply with the contact switch closure, almost there is not the start-up time, has guaranteed that the electric wire netting can last the power supply always, and switches fast, the energy environmental protection.
Preferably, the method comprises the following steps:
s1: detecting whether the bus supplies power, if the bus fails, starting a standby power supply, and entering step S2, and if the bus is normal, entering step S2;
s2: detecting whether the voltage is smaller than the rated voltage, if the voltage is normal, ending the detection, and if the voltage is smaller than the rated voltage, entering the step S3;
s3: detecting whether the frequency is normal, if the frequency is normal, entering a step S41, if the frequency is abnormal, controlling the frequency of the generator set by the frequency converter, and then entering a step S42;
s41: compensating power supply of a power supply to enable the voltage to reach the rated voltage of the power supply, and finishing detection;
s42: and detecting whether the voltage is smaller than the rated voltage again, if the voltage is normal, finishing the detection, and if the voltage is smaller than the rated voltage, supplying power by using a compensation power supply to enable the voltage to reach the rated voltage of the power supply, and finishing the detection.
Firstly, detecting whether a bus supplies power, ensuring that the power supply of a power grid is continuous all the time, and if the bus does not supply power, using a standby power supply for supplying power; detecting whether the voltage output by the power grid is smaller than the rated voltage, if not, indicating that the power supply is normal, ending the detection, and performing the first step of circular detection; if the output voltage of the power grid is smaller than the rated voltage, detecting whether the frequency is the same as the rated frequency, if the frequency reaches the rated frequency, indicating that the power consumption of the load is too large and the voltage output by the bus does not support the load enough, adding a compensation power supply into the alternating current power grid for supplying power, so that the voltage output by the alternating current power grid reaches the rated voltage; if the result of the frequency detection is different from the rated voltage, the power generation capacity of the generator set is smaller than the required power generation capacity, the power generation frequency of the generator set is changed through the frequency changer, the power generation capacity of the generator set is improved, active power and reactive power are balanced, then whether the output voltage reaches the rated voltage is detected again, if the power generation capacity of the generator set is improved, the output voltage reaches the rated voltage, the detection is finished, if the output voltage is still smaller than the rated voltage, a compensation power supply is used to be added into the alternating current power grid for supplying power, the output voltage of the alternating current power grid reaches the rated voltage, and then the detection and adjustment are finished.
Preferably, in step S2, if the voltage is greater than the rated voltage and the compensation power supply is less than the first power threshold, the first contact of the control switch is closed to charge the compensation power supply. When the output voltage is detected, if the output voltage is greater than the rated voltage, the situation that redundant electric energy exists is indicated, at the moment, the electric quantity of the compensation power supply is detected, and if the electric quantity of the compensation power supply is smaller than a first electric quantity threshold value, namely 90% of the total electric quantity of the compensation power supply, the control switch is turned to the first contact, and the compensation power supply is controlled to be charged. The compensation power supply is charged by utilizing redundant electric energy, so that the electric energy can be saved, the sufficient electric quantity of the compensation power supply can be ensured, and the sufficient electric quantity can be provided for the alternating current power grid when the compensation power supply is needed to supply power.
Preferably, the step S41 includes the following steps:
s411: judging the electric quantity of the compensation power supply, if the electric quantity of the compensation power supply is smaller than a second electric quantity threshold value, closing a first contact of a control switch, charging the compensation power supply, and if the electric quantity of the compensation power supply is larger than the second electric quantity threshold value, entering a step S412;
s412: and closing the third contact of the control switch, compensating the power supply of the power supply, enabling the voltage to reach the rated voltage of the power supply, and ending the detection.
When the compensation power supply supplies power to the alternating current power grid, whether the compensation power supply has enough electric quantity to supply power to the alternating current power grid is checked firstly, if the electric quantity of the compensation power supply is smaller than a second electric quantity threshold value, namely 25% of the total electric quantity of the compensation power supply, the electric quantity of the compensation power supply is not enough to supply power to the alternating current power grid, a first contact of a control switch is closed to charge the compensation power supply, if the electric quantity of the compensation power supply is larger than the second electric quantity threshold value, the compensation power supply has enough electric quantity to supply power to the alternating current power grid, the control switch is turned to a third contact, and the compensation power supply supplies power to the alternating current power grid. The compensation power supply is ensured to have enough electric quantity to supply power for an alternating current power grid, the stability of the voltage is ensured when the compensation power supply is used, and the interference of low electric quantity cannot occur.
Preferably, the step S42 includes the following steps:
s421: judging whether the voltage is smaller than the rated voltage, if the voltage is normal, finishing the detection, and if the voltage is smaller than the rated voltage, entering the step S422;
s422: judging the electric quantity of the compensation power supply, if the electric quantity of the compensation power supply is smaller than a second electric quantity threshold value, closing a first contact of a control switch, charging the compensation power supply, and if the electric quantity of the compensation power supply is larger than the second electric quantity threshold value, entering a step S423;
s423: and closing the third contact of the control switch, compensating the power supply of the power supply, enabling the voltage to reach the rated voltage of the power supply, and ending the detection.
Before the compensation power supply supplies power to the alternating current power grid, whether the compensation power supply has enough electric quantity to supply power to the alternating current power grid is checked, if the electric quantity of the compensation power supply is smaller than a second electric quantity threshold value, namely 25% of the total electric quantity of the compensation power supply, the electric quantity of the compensation power supply is not enough to supply power to the alternating current power grid, a first contact of a control switch is closed to charge the compensation power supply, if the electric quantity of the compensation power supply is larger than the second electric quantity threshold value, the compensation power supply has enough electric quantity to supply power to the alternating current power grid, the control switch is turned to a third contact, and the compensation power supply supplies power to the alternating current power grid. The compensation power supply is ensured to have enough electric quantity to supply power for an alternating current power grid, the stability of the voltage is ensured when the compensation power supply is used, and the interference of low electric quantity cannot occur.
The invention has the beneficial effects that:
1. the standby power supply is used, so that continuous power supply and uninterrupted power supply of an alternating current power grid are ensured, and continuous and stable power supply is ensured.
2. And the third bus is used as a standby power supply, so that the switching-in speed of the standby power supply is improved, and the continuous and stable power supply of an alternating current power grid is ensured.
3. And a compensation power supply is used, and the output voltage is kept to be not less than the rated voltage according to the feedback of the voltage sensor, so that the stability of the output voltage is ensured.
4. When the output voltage is higher than the rated voltage, the compensation power supply is charged, so that the electric energy is saved, and the compensation power supply is ensured to have enough electric quantity to supply power for an alternating current power grid.
5. The frequency converter controls the frequency of the generator set, ensures that the generated energy of the generator set meets the demand, and ensures the balance of active power and reactive power.
Drawings
Fig. 1 is a block diagram of a power supply system connection structure according to the present invention.
Fig. 2 is a connection diagram of an ac power grid and a backup power source in a first embodiment of the present invention.
Fig. 3 is a connection diagram of an ac power grid and a backup power source in the second embodiment of the present invention.
Fig. 4 is a circuit diagram of a compensated power supply of the present invention.
Fig. 5 is a logic circuit diagram of a control switch of the present invention.
Fig. 6 is a flow chart of a method of the present invention.
In the figure, 1, a generator set, 2, an alternating current power grid, 21, a tie switch, 3, a standby power supply, 31, a diesel generator, 32, a third bus, 4, a load, 5, a voltage sensor, 6, a frequency detector, 7, a control switch, 8, a compensation power supply, 81, a rectifying circuit, 82, an inverter circuit, 83, a battery pack and 9, a frequency converter are arranged.
Detailed Description
The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings.
The first embodiment is as follows:
the power supply system for stable power supply of the present embodiment, as shown in fig. 1, includes a generator set 1, an ac power grid 2, a load 4, and a backup power supply 3 connected to the ac power grid, where the backup power supply 3 may be a diesel generator 31, or may be another third bus 32; the generator set 1 generates electricity according to a certain frequency, the alternating current power grid 2 outputs the generated electricity to a load 4, and the load 4 comprises a lower-level distribution network and field equipment. The power supply system also comprises a voltage sensor 5 for detecting the voltage output by the alternating current power grid 2, a frequency detector 6 for detecting the frequency, a compensation power supply 8, a frequency converter 9 and a control switch 7, wherein the compensation power supply 8 is connected with the alternating current power grid 2 through the control switch 7, the control switch 7 receives the detected voltage, and the compensation power supply 8 is controlled to supply power to the alternating current power grid 2 or charge the alternating current power grid 2; the frequency converter 9 receives the detected frequency and controls the power generation frequency of the generator set 1.
Under normal conditions, the generator set generates electricity, and the alternating current power grid transmits the electric energy to a load. When the alternating current power grid or the generator set breaks down and needs to be powered off, the standby power supply replaces the alternating current power grid to supply power to the load, and time is provided for maintenance. When the detected output voltage is lower than the rated voltage, the control switch controls the compensation power supply to supply power to the load until the voltage reaches the rated voltage. When the detected frequency is different from the rated frequency, the frequency converter controls the power generation frequency of the generator set, so that the frequency reaches the stable rated frequency, and the motor is synchronously balanced. The system can guarantee continuous power supply, so that electric energy is always continuous, the quality of output electric energy is guaranteed, the voltage and the frequency reach rated values, and the balance value of active power and reactive power is achieved. The power supply system is stable in power supply and stable in power supply quality.
As shown in fig. 2, the ac power grid 2 includes a first bus bar and a second bus bar, which are connected to each other by a tie switch 21, and the first bus bar and the second bus bar are each connected to a different load 4. The standby power supply 3 is a diesel generator 31, and the output end of the diesel generator is respectively connected with the first bus and the second bus. The first bus and the second bus form a ring network structure through two tie switches 21. The first bus and the second bus share different loads 4, so that the respective pressure of the two buses is reduced, enough margin can drive more loads, and the safety and stability of a power grid are ensured; the interconnection switch 21 is normally disconnected, when one bus fails and needs to be maintained, the interconnection switch 21 is closed, the other bus supplies power for the two paths of loads 4, the temporary uninterruptible power of the loads 4 is guaranteed, and time is provided for adding the standby power supply 3 and maintaining the failed bus. And uninterrupted power supply of the power grid is ensured.
As shown in fig. 4, the compensation power supply includes a rectifying circuit 81, an inverter circuit 82, and a battery pack 83 with a meter; the battery pack 83 may be an uninterruptible power supply UPS, a lead-zinc battery pack, or a super capacitor. The control switch is a single-pole three-position switch, and the switch comprises a first contact a, a second contact b and a third contact c. The first contact a and the third contact c are electromagnetic contacts. The rectifying circuit 81 is a full-bridge rectifying circuit composed of four thyristors and comprises a thyristor D1, a thyristor D2, a thyristor D3 and a thyristor D4, the cathodes of the thyristor D1 and the thyristor D2 are connected, the anode of the thyristor D3 and the anode of the thyristor D4 are connected, the cathode of the thyristor D3 is connected with the anode of the thyristor D1, the cathode of the thyristor D4 is connected with the anode of the thyristor D2, the cathode of the thyristor D2 is connected with the anode of the battery pack 83, and the anode of the thyristor D4 is connected with the cathode of the battery pack 83. The inverter circuit 82 is a full-bridge inverter circuit formed by four thyristors and comprises a thyristor D5, a thyristor D6, a thyristor D7 and a thyristor D8, the cathodes of the thyristor D7 and the thyristor D8 are connected, the anode of the thyristor D5 and the anode of the thyristor D6 are connected, the cathode of the thyristor D5 is connected with the anode of the thyristor D7, the cathode of the thyristor D6 is connected with the anode of the thyristor D8, the anode of the thyristor D6 is connected with the anode of the battery pack 83, and the cathode of the thyristor D8 is connected with the cathode of the battery pack 83. The anodes of the thyristor D1 and the thyristor D2 in the rectifying circuit 81 are used as the input ends of the rectifying circuit 81 and are connected with an alternating current network, the anode of the thyristor D2 is connected with a zero line, and the anode of the thyristor D1 is connected with the first contact a of the control switch 7. And cathodes of a thyristor D5 and a thyristor D6 in the inverter circuit 82 are used as output ends of the inverter circuit 82 and are connected with an alternating current power grid, a cathode of the thyristor D5 is connected with a zero line, and a cathode of the thyristor D6 is connected with a third contact c of the control switch 7. The second contact b of the control switch 7 is suspended, and the control switch 7 is connected with the live wire.
The rectification circuit changes alternating current into direct current to charge the battery pack, the inverter circuit converts the direct current in the battery pack into the alternating current, and when the voltage in the alternating current power grid is insufficient, the voltage of the alternating current power grid is increased. The battery pack charge quantity detection device can monitor the electric quantity of the battery pack, and the control switch judges whether the compensation power supply is in a charging mode, a discharging mode or a standby mode according to the received voltage comparison signal and electric quantity comparison signal. The state of the compensation power supply can be automatically controlled according to the electric quantity of the compensation power supply and the output voltage, the compensation power supply is guaranteed to have enough electric quantity to be the compensation voltage of the alternating current power grid, the stability of the output voltage is further guaranteed, and the output voltage is not lower than the rated voltage.
As shown in fig. 5, the control switch includes a logic control circuit including a first electrical quantity comparator U6, a second electrical quantity comparator U7, a voltage comparator U5, an and gate U1, an and gate U2, a not gate U3, and a not gate U4; the positive input end of the voltage comparator U5 is rated voltage Vref, the negative input end is connected with the voltage sensor 5 and receives the output voltage V of the power grid, the output end is connected with the input end of the NOT gate U3, the output end of the NOT gate U3 is connected with one input end of the AND gate U1, and the output end of the voltage comparator U5 is connected with one input end of the AND gate U2; the positive input end of the first electric quantity comparator U6 is a first electric quantity threshold Q1, the negative input end is connected with the output end of the electricity meter and receives the electric quantity Q of the compensation power supply 8, the output end of the first electric quantity comparator U6 is connected with the other input end of the AND gate U1, and the output end of the AND gate U1 is connected with the first contact a of the control switch 7; the positive input end of the second electric quantity comparator U7 is a second electric quantity threshold Q2, the negative input end is connected with the output end of the electricity meter, the electric quantity Q of the compensation power supply 8 is received, the output end is connected with the first contact a of the control switch 7, the output end of the second electric quantity comparator U7 is connected with the input end of the not gate U4, the output end of the not gate U4 is connected with the other input end of the and gate U2, and the output end of the and gate U2 is connected with the third contact c of the control switch 7. The first threshold Q1 is 90% of the total charge of the compensation power supply 8, and the second threshold Q2 is 25% of the total charge of the compensation power supply. The first power threshold Q1, the second power threshold Q2 and the nominal voltage Vref are values that are considered to be set. The compensation power supply 8 is ensured to have enough electric quantity to compensate the voltage of the alternating current power grid 2, power is not supplied when the electric quantity is insufficient, the output of the alternating current power grid 2 is ensured not to be interfered, and the output of the alternating current power grid 2 is ensured to be a stable value.
In the method for stably supplying power of this embodiment, as shown in fig. 6, the power supply system includes the following steps:
s1: and detecting whether the bus supplies power, starting a standby power supply if the bus fails, and entering the step S2, and entering the step S2 if the bus is normal.
Whether the bus supplies power is detected firstly, the power supply of a power grid is ensured to be continuous all the time, and if the bus does not supply power, the standby power supply 3 is used for supplying power.
S2: detecting whether the voltage is smaller than the rated voltage, if the voltage is normal, ending the detection, and if the voltage is smaller than the rated voltage, entering the step S3;
and detecting whether the voltage V output by the power grid is smaller than the rated voltage Vref, wherein in the embodiment, the rated voltage is 35kV, the voltage sensor detects an output signal and transmits the output signal to a standard signal, so that the rated voltage Vref is 17mV, and if the output voltage is 35kV, the detected voltage is 17mV after transmission. If the voltage V is not less than the rated voltage Vref, the power supply is normal, the detection is finished, and the first step of circular detection is carried out; if the output voltage V of the power grid is less than the rated voltage Vref, it is detected whether the frequency is the same as the rated frequency, in this embodiment, the rated frequency is 50Hz, the upper limit of the normal range of frequency detection is 52Hz, the lower limit of the normal range of frequency detection is 48Hz, if the detected frequency is between 48Hz and 52Hz, it is a normal value, and if it exceeds 52Hz or is lower than 48Hz, it is abnormal.
If the voltage V is greater than the rated voltage Vref and the compensation power supply Q is less than the first power threshold Q1, the first contact a of the control switch 7 is closed and the compensation power supply 8 is charged. When the output voltage V is detected, if the output voltage V is greater than the rated voltage Vref, it indicates that there is excess power, and at this time, the power quantity of the compensation power supply 8 is detected, and if the power quantity Q of the compensation power supply 8 is less than the first power quantity threshold value Q1, i.e. 90% of the total power quantity of the compensation power supply 8, the control switch 7 is opened to the first contact a, and the compensation power supply is controlled to be charged. The surplus electric energy is used for charging the compensation power supply 8, the electric energy can be saved, the sufficient electric quantity Q of the compensation power supply 8 can be guaranteed, and when the compensation power supply 8 is needed to supply power, the sufficient electric quantity can be provided for the electric energy provided by the alternating current power grid 2.
S3: detecting whether the frequency is normal, if the frequency is normal, entering step S41, if the frequency is abnormal, controlling the frequency of the generator set 1 by the frequency converter 9, and then entering step S42;
s41: the compensation power supply 8 supplies power to enable the voltage V to reach the rated voltage Vref of the power supply, and detection is finished;
detecting whether the frequency is the same as the rated frequency, if the frequency reaches the rated frequency, indicating that the power consumption of the load 4 is too large and the voltage output by the bus does not support the load enough, adding a compensation power supply 8 into the alternating current power grid 2 for supplying power, so that the voltage V output by the alternating current power grid 2 reaches the rated voltage Vref; if the result of the frequency detection is different from the rated frequency, the power generation capacity of the generator set 1 is smaller than the required power generation capacity, the power generation frequency of the generator set is changed through the frequency changer 9, the power generation capacity of the generator set 1 is improved, and the active power and the reactive power are balanced.
S411: judging the electric quantity of the compensation power supply, if the electric quantity of the compensation power supply is smaller than a second electric quantity threshold value Q2, closing a first contact a of a control switch 7, charging the compensation power supply 8, and if the electric quantity Q of the compensation power supply 8 is larger than a second electric quantity threshold value Q2, entering the step S412;
s412: and closing the third contact c of the control switch 7, supplying power by the compensation power supply 8, enabling the voltage V to reach the rated voltage Vref of power supply, and finishing detection.
S42: and detecting whether the voltage V is smaller than the rated voltage Vref again, finishing the detection if the voltage V is normal, and supplying power by using the compensation power supply 8 if the voltage V is smaller than the rated voltage Vref to ensure that the voltage V reaches the rated voltage Vref of the power supply, and finishing the detection.
And detecting whether the output voltage V reaches the rated voltage Vref again, finishing the detection if the output voltage V reaches the rated voltage Vref after the power generation capacity of the generator set 1 is improved, adding the compensation power supply 8 into the alternating current power grid 2 for supplying power if the output voltage V is still less than the rated voltage Vref, and finishing the detection and adjustment.
S421: judging whether the voltage V is smaller than the rated voltage Vref, if the voltage V is normal, finishing the detection, and if the voltage V is smaller than the rated voltage Vref, entering the step S422;
s422: judging the electric quantity Q of the compensation power supply, if the electric quantity Q of the compensation power supply 8 is smaller than a second electric quantity threshold value Q2, closing a first contact a of a control switch 7, charging the compensation power supply 8, and if the electric quantity Q of the compensation power supply 8 is larger than a second electric quantity threshold value Q2, entering a step S423;
s423: and closing the third contact c of the control switch 7, supplying power by the compensation power supply 8, enabling the voltage V to reach the rated voltage Vref of power supply, and finishing detection.
Before the compensation power supply 8 supplies power to the alternating current power grid 2, whether the compensation power supply 8 has enough electric quantity Q to supply power to the alternating current power grid 2 is checked, if the electric quantity Q of the compensation power supply 8 is smaller than a second electric quantity threshold Q2, namely 25% of the total electric quantity of the compensation power supply 8, it is indicated that the electric quantity Q of the compensation power supply 8 is not enough to supply power to the alternating current power grid 2, a first contact a of a control switch 7 is closed to charge the compensation power supply 8, if the electric quantity Q of the compensation power supply 8 is larger than a second electric quantity threshold Q2, it is indicated that the compensation power supply 8 has enough electric quantity Q to supply power to the alternating current power grid 2, the control switch 7 turns on a third contact c, and the compensation power supply 8 supplies power to the alternating current power grid 2. The compensation power supply 8 is ensured to have enough electric quantity Q to supply power for the alternating current power grid 2, and the stability of the voltage V is ensured without the interference of low electric quantity when the compensation power supply 8 is used.
Example two:
as shown in fig. 3, the ac power grid includes a first bus and a second bus, the first bus and the second bus are connected by a tie switch 21, and the first bus and the second bus are connected to different loads 4; the standby power supply 3 is a third bus bar 32, the third bus bar 32 is respectively connected with the first bus bar and the second bus bar through a tie switch 21, and the third bus bar 32 is in a hot standby state. The time of using third generating line 32 to insert is short, and hot standby always just needs to be closed with interconnection switch 21 and just can be for alternating current electric wire netting 2 power supply, has hardly the boot time, has guaranteed that the electric wire netting can last the power supply always, and switches fast, the energy environmental protection. Compared with the first embodiment, the embodiment changes the selection of the standby power supply 3 and the connection mode with the alternating current power grid 2, and the rest is the same as the first embodiment.
The invention uses the standby power supply, ensures the continuous power supply and the uninterrupted power supply of the alternating current power grid, and ensures the continuous and stable power supply. And the third bus is used as a standby power supply, so that the switching-in speed of the standby power supply is improved, and the continuous and stable power supply of an alternating current power grid is ensured. And a compensation power supply is used, and the output voltage is kept to be not less than the rated voltage according to the feedback of the voltage sensor, so that the stability of the output voltage is ensured. When the output voltage is higher than the rated voltage, the compensation power supply is charged, so that the electric energy is saved, and the compensation power supply is ensured to have enough electric quantity to supply power for an alternating current power grid. The frequency converter controls the frequency of the generator set, ensures that the generated energy of the generator set meets the demand, and ensures the balance of active power and reactive power. The stability of the power supply is ensured, and the stability of the quality of the power supply is ensured.
Claims (9)
1. A power supply system for stable power supply comprises a generator set (1), an alternating current power grid (2), a load (4) and a standby power supply (3) connected with the alternating current power grid (2), wherein the alternating current power grid (2) outputs electricity to the load (4), and the load (4) comprises a lower-level power distribution network and field equipment; characterized in that the power supply system also comprises
A voltage sensor (5) for detecting the voltage output by the AC power grid (2);
a frequency detector (6) for detecting the frequency output by the AC power network (2) when the voltage output by the AC power network (2) is less than a rated voltage threshold value;
a compensation power supply (8) connected to the AC power grid (2);
the control switch (7) receives the detected voltage, and controls the compensation power supply (8) to charge when the output voltage of the alternating current power grid (2) is greater than a rated voltage threshold and the electric quantity of the compensation power supply (8) is less than a first electric quantity threshold; when the output voltage of the alternating current power grid (2) is smaller than a rated voltage threshold value, the output frequency is within a rated frequency threshold value, and the electric quantity of the compensation power supply (8) is larger than a second electric quantity threshold value, or when the electric quantity of the compensation power supply (8) is smaller than the second electric quantity threshold value, the compensation power supply is controlled to be charged;
and the frequency converter (9) receives the detected frequency and controls the power generation frequency of the generator set (1).
2. A stable power supply system according to claim 1, wherein said compensation power supply (8) comprises a rectifying circuit (81), an inverter circuit (82) and a battery pack (83) with a charge meter; the rectification circuit (81) is a full-bridge rectification circuit (81) formed by four thyristors, and the inverter circuit (82) is a full-bridge inverter circuit (82) formed by four thyristors; the input end of the rectifying circuit (81) is connected with the alternating current power grid (2), and the output end of the rectifying circuit (81) is connected with the battery pack (83); the input end of the inverter circuit (82) is connected with the battery pack (83), and the output end of the inverter circuit (82) is connected with the alternating current power grid (2).
3. A stable power supply system according to claim 2, characterized in that said control switch (7) is a single-pole three-position switch; the first contact is arranged between the alternating current power grid (2) and the input end of the rectifying circuit (81), the second contact is suspended, and the third contact is arranged between the alternating current power grid (2) and the output end of the inverter circuit (82); the first contact and the third contact are electromagnetic contacts.
4. A stably powered power supply system according to claim 1, characterized in that said control switch (7) comprises a logic control circuit comprising a first power comparator, a second power comparator, a voltage comparator, an and gate U1, an and gate U2, an not gate U3 and an not gate U4; the positive input end of the voltage comparator is rated voltage, the negative input end of the voltage comparator is connected with the voltage sensor (5), the output end of the voltage comparator is connected with the input end of the NOT gate U3, the output end of the NOT gate U3 is connected with one input end of the AND gate U1, and the output end of the voltage comparator is connected with one input end of the AND gate U2; the positive input end of the first electricity quantity comparator is a first electricity quantity threshold, the negative input end of the first electricity quantity comparator is connected with the output end of the electricity meter, the output end of the first electricity quantity comparator is connected with the other input end of the AND gate U1, and the output end of the AND gate U1 is connected with a first contact of the control switch (7); the positive input end of the second electric quantity comparator is a second electric quantity threshold, the negative input end of the second electric quantity comparator is connected with the output end of the electric quantity meter, the output end of the second electric quantity comparator is connected with the first contact of the control switch (7), the output end of the second electric quantity comparator is connected with the input end of the NOT gate U4, the output end of the NOT gate U4 is connected with the other input end of the AND gate U2, and the output end of the AND gate U2 is connected with the third contact of the control switch (7).
5. A mains system for stable power supply according to claim 1, characterized in that the ac network (2) comprises a first and a second bus bar, connected by a tie switch (21), the first and the second bus bar being connected to different loads (4); the standby power supply (3) is a diesel generator (31), and the output end of the diesel generator (31) is respectively connected with the first bus and the second bus.
6. A mains system for stable power supply according to claim 1, characterized in that the ac network (2) comprises a first and a second bus bar, connected by a tie switch (21), the first and the second bus bar being connected to different loads (4); the standby power supply (3) is a third bus (32), the third bus (32) is respectively connected with the first bus and the second bus through a tie switch (21), and the third bus (32) is in hot standby.
7. A method for stably supplying power by using the power supply system for stably supplying power of any one of claims 1 to 6, characterized by comprising the following steps:
s1: detecting whether the bus supplies power, if the bus fails, starting a standby power supply (3), entering step S2, and if the bus is normal, entering step S2;
s2: detecting whether the voltage is smaller than the rated voltage, if the voltage is normal, ending the detection, and if the voltage is smaller than the rated voltage, entering the step S3;
s3: detecting whether the frequency is normal, if the frequency is normal, entering step S411, if the frequency is abnormal, controlling the frequency of the generator set (1) by the frequency converter (9), and then entering step S42;
s411: judging the electric quantity of the compensation power supply (8), if the electric quantity of the compensation power supply (8) is smaller than a second electric quantity threshold value, closing the first end of the control switch (7), charging the compensation power supply (8), and if the electric quantity of the compensation power supply (8) is larger than the second electric quantity threshold value, entering the step S412;
s412: closing the third end of the control switch (7), supplying power by the compensation power supply (8), enabling the voltage to reach the rated voltage of the power supply, and ending the detection;
s42: and detecting whether the voltage is smaller than the rated voltage again, if the voltage is normal, finishing the detection, and if the voltage is smaller than the rated voltage, supplying power by using a compensation power supply (8) to enable the voltage to reach the rated voltage of the power supply, and finishing the detection.
8. The method according to claim 7, wherein in step S2, if the voltage level is greater than the rated voltage and the compensation power supply (8) is less than the first threshold, the first terminal of the control switch (7) is closed and the compensation power supply (8) is charged.
9. The method of claim 7, wherein the step S42 includes the steps of:
s421: judging whether the voltage is smaller than the rated voltage, if the voltage is normal, finishing the detection, and if the voltage is smaller than the rated voltage, entering the step S422;
s422: judging the electric quantity of the compensation power supply (8), if the electric quantity of the compensation power supply (8) is smaller than a second electric quantity threshold value, closing the first end of the control switch (7), charging the compensation power supply (8), and if the electric quantity of the compensation power supply (8) is larger than the second electric quantity threshold value, entering a step S423;
s423: and closing the third end of the control switch (7), supplying power by the compensation power supply (8), enabling the voltage to reach the rated voltage of the power supply, and finishing detection.
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