CN110212543B - Power spring system considering non-critical load and control method thereof - Google Patents

Power spring system considering non-critical load and control method thereof Download PDF

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CN110212543B
CN110212543B CN201910378003.1A CN201910378003A CN110212543B CN 110212543 B CN110212543 B CN 110212543B CN 201910378003 A CN201910378003 A CN 201910378003A CN 110212543 B CN110212543 B CN 110212543B
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李勇
林锦杰
刘乾易
张靖
王绍阳
曹一家
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Hunan University
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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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

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  • Power Engineering (AREA)
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Abstract

The invention discloses a power spring system giving consideration to non-critical loads and a control method thereof. The power spring system can detect the state of the non-critical load through the sensor so as to switch the working state of the power spring, and solves the problem that the power spring cannot run when the non-critical load is not connected or fails. Meanwhile, aiming at the problem that the voltage of a non-critical load in the power spring system possibly exceeds the limit operation range of the non-critical load, the invention provides a control method which can inhibit the voltage fluctuation of the critical load and can adjust the voltage of the non-critical load under the condition that the non-critical load exceeds the limit operation range, so that the non-critical load cannot be damaged or cannot normally work due to the fact that the non-critical load exceeds the limit operation range when the system works.

Description

Power spring system giving consideration to non-critical load and control method thereof
Technical Field
The invention relates to the application field of power electronic devices in a power system, in particular to a power spring system giving consideration to non-critical loads.
Background
With the continuous development of new energy power generation technology, the proportion of renewable energy sources such as wind energy and the like connected into a power grid is increased year by year. The power generation is difficult to predict due to the intermittency and uncertainty inherent in renewable energy sources. The supply and demand relationship of the traditional power system is in the face of high-permeability renewable energy access, the problems of voltage fluctuation, flicker, harmonic pollution and other electric energy quality can be faced, and the safe and stable operation of the power system is endangered. Especially for a micro-grid, due to the limited self-regulation capability, voltage fluctuation can bring adverse effects to other electric equipment. Especially, the unstable operation of some precision devices with strict requirements on the input voltage range, such as vital sign detection devices in hospitals, may cause huge loss of life and property. The electric spring is provided, so that the problems can be effectively solved. Loads can be classified as critical loads and non-critical loads depending on how sensitive the load is to voltage. The voltage fluctuation on the key load can be restrained through reactive compensation, and the fluctuation is transferred to the non-key load, so that the electric energy quality on the key load is improved.
The traditional power spring control can realize reactive compensation by adjusting the output voltage of the power spring, stabilize the voltage on a key load when the power voltage fluctuates, and simultaneously transfer the voltage fluctuation to a non-key load, thereby realizing the purpose of improving the quality of electric energy on the key load.
The traditional scheme does not consider the condition that the non-critical load is in failure or is not connected, and the power spring cannot work normally. At the same time, non-critical loads are ignored, taking into account only the quality of the electrical energy on critical loads. Although the non-critical load allows a wide range of operating voltages, it cannot be sacrificed without limitation, and must therefore be adjusted when it exceeds its voltage fluctuation range.
Disclosure of Invention
The present invention is directed to overcoming the above-mentioned drawbacks of the prior art, and to provide an electric spring system and a control method thereof that are compatible with non-critical loads. On one hand, the power spring system considering the non-critical load and the control method thereof provided by the invention can enable the power spring to continue to work normally through the control switch when the non-critical load is not accessed or fails. On the other hand, when the voltage on the key load fluctuates, the power spring can adjust the voltage by a reactive compensation method; meanwhile, the voltage on the non-critical load can be adjusted when exceeding the maximum voltage fluctuation range accepted by the non-critical load.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a power spring system for non-critical loads comprises a switch drive circuit, a bidirectional DC power supply V DC The single-phase controlled voltage source type inverter with two-level topology, and the LC low-pass filter for filtering high-frequency components in the output voltage of the inverter; the specific connection relationship of the system is as follows: bidirectional DC power supply V DC The single-phase controlled voltage source type inverter with the two-level topology and the LC low-pass filter form a power spring together; network side power supply V G Through line impedance L 0 And R 0 Connected to the publicThe point of connection PCC, the power spring passes through the filter capacitor C and the non-critical load Z NCL After series connection, the same key load Z CL Parallel to the point of common coupling PCC; the switch S2 is connected with the filter capacitor C in series; the S1 is used as a bypass switch and can switch the serial part of the switch S2 and the filter capacitor C; switch S4 and non-critical load Z NCL Are connected in series; the switch S3 as a bypass switch can be used for switching the switch S4 and the non-critical load Z NCL Switching the serial part; a controller in the inverter acquires a sensor signal to determine a working state and drives a switch to act through a driving circuit; when the switches S2 and S4 are closed and the switch S3 is opened, the bypass switch S1 is controlled to switch the power spring; when a non-critical load is not accessed or the non-critical load fails, the switches S1, S2 and S4 are all disconnected, and the power spring is directly connected with the critical load in parallel to the PCC to ensure that the power spring continues to normally work; when the power spring part fails, the power spring is taken out of operation, embodied as a non-critical load Z NCL When the switch is switched on and has no fault, the switches S1 and S4 are closed, the switches S2 and S3 are opened, otherwise, the switches S1, S2, S3 and S4 are all opened.
In a further development, the controller in the inverter detects the flow through the non-critical load Z by means of a current sensor NCL To determine the non-critical load Z NCL Access status and whether a failure has occurred.
Further improvement, by compensating reactive power, stabilizing the critical load Z CL Voltage V across S (ii) a When a non-critical load Z is detected NCL When the voltage at two ends exceeds the maximum fluctuation range, the non-critical load Z is limited by compensating the active power NCL Voltage V across NCL Fluctuating.
The control method of the power spring system for considering the non-critical load comprises the following steps:
(1) By collecting the current i flowing through the branch of the power spring 2 Generating a synchronous phase angle through a phase-locked loop to provide a phase reference for a control circuit;
(2) The voltage sensor collects the voltage signal V of the public connecting point S Reference signal V S_ref Is subtracted to obtain an error signal e 0 Will error signal e 0 Transmitting the reference signal into a proportional integral PI controller, and performing amplitude limiting processing to obtain a reference signal V of q-axis voltage ES_q ；
(3) By detecting non-critical loads Z NCL Voltage V above NCL And determining the voltage V NCL Whether the maximum fluctuation range (V) of the non-critical load itself is exceeded lower ,V upper ) (ii) a Loading a non-critical load Z NCL Voltage V on NCL Upper limit of voltage V upper Lower voltage limit V lower Sending the signal into a comparator; when V is 0 Below the lower limit, V lower And V NCL Differencing to obtain an error signal e 1 (ii) a When V is NCL Above the upper limit, V upper And V NCL Differencing to obtain an error signal e 1 (ii) a If the maximum fluctuation range (V) is not exceeded lower ,V upper ) If the comparator does not operate, the error signal e is outputted 1 0, i.e. no conditioning; error signal e 1 Transmitting the voltage into a proportional integral PI controller and carrying out amplitude limiting treatment to obtain a reference signal V of d-axis voltage ES_d ；
(4) Will V ES_d 、V ES_q After conversion, the inverter output reference voltage V is obtained after amplitude limiting treatment ES_ref ；
(5) Collecting voltage V on filter capacitor ES A V is measured ES_ref Error signal is obtained by subtracting the reference voltage from the reference voltage and is transmitted to the proportional resonant controller to obtain the output reference voltage V of the inverter ES_out ；
(6) The reference voltage V is used ES_out The modulation wave as SPWM is compared with a triangular carrier wave, and a driving signal for controlling the on-off of a switch tube in the single-phase voltage source inverter is obtained at the intersection point moment of the modulation wave and the carrier wave; when a non-critical load is connected and no fault occurs, the power P in the system satisfies the following formula:
Figure GDA0002104084010000021
P＝P NCL +P CL (2)
Z NCL is a non-critical load; z is a linear or branched member CL Is a critical load; v S Being the voltage of the point of common coupling PCC, also the critical load Z CL Voltage at two ends; v ES Outputting voltage for the power spring, namely the voltage on the filter capacitor; p NCL Active power consumed for non-critical loads; p CL Active power consumed for critical loads.
Further improvement, in the maximum fluctuation range (V) of the non-critical load itself lower ,V upper ) The default upper limit is equal to 1.2 times of the rated voltage, and the default lower limit is equal to 0.8 times of the rated voltage, which can be changed according to actual needs.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the power spring system giving consideration to the non-critical load and the control method thereof, the power spring can still keep normal work when the non-critical load is not accessed or fails in the operation process, and the voltage on the critical load is adjusted to ensure that the voltage fluctuation on the critical load is effectively inhibited.
(2) According to the power spring system giving consideration to the non-critical load and the control method thereof, when the voltage fluctuates, the voltage fluctuation on the critical load can be restrained through reactive compensation, and the fluctuation is transmitted to the non-critical load. The control method provided by the invention considers that the voltage fluctuation on the non-critical load can exceed the maximum range in which the non-critical load can operate, and the non-critical load can be caused to be out of work or damaged, so that a voltage ring is additionally designed to regulate the voltage on the non-critical load. When the sensor detects that the voltage across the non-critical load exceeds the upper limit of its maximum operating range or falls below the lower limit of the maximum operating range, its operating voltage will be limited within the maximum operating range by regulating the real power. The voltage on the key load can be improved, the voltage on the non-key load can be considered, and the safe and stable operation of the system can be guaranteed.
Drawings
FIG. 1 is a block diagram of an electrical spring system for non-critical loads in accordance with the present invention
FIG. 2 is a control block diagram of a control method of an electric spring system with consideration of non-critical loads according to the present invention
FIG. 3 is a flowchart illustrating an implementation of the power spring system and the control method thereof considering non-critical loads according to the present invention
Fig. 4 is a phasor diagram of parameters of each part in a circuit under a resistive load condition after a control method of a power spring system considering non-critical loads is adopted in the invention.
Detailed Description
The present invention will be further described with reference to the accompanying drawings.
The following is a preferred example of a non-critical load compatible power spring system of the present invention and is not intended to limit the scope of the invention.
Referring to fig. 1, a power spring system for non-critical loads is disclosed, which includes a switch driving circuit, a bi-directional dc power supply V DC The single-phase controlled voltage source type inverter with two-level topology, and the LC low-pass filter for filtering high-frequency components in the output voltage of the inverter; the specific connection relationship of the system is as follows: bidirectional DC power supply V DC The single-phase controlled voltage source type inverter with the two-level topology and the LC low-pass filter jointly form a power spring; network side power supply V G Through line impedance L 0 And R 0 Connected to a point of common coupling PCC, the power spring passing through a filter capacitor C and a non-critical load Z NCL After series connection, the same key load Z CL Parallel to a common connection point PCC; the switch S2 is connected with the filter capacitor C in series; the S1 is used as a bypass switch and can switch the serial part of the switch S2 and the filter capacitor C; switch S4 and non-critical load Z NCL Are connected in series; the switch S3 as a bypass switch can be used for switching the switch S4 and the non-critical load Z NCL Switching the serial part; a controller in the inverter acquires a sensor signal to determine the working state, and drives the switch to act through a driving circuit.
Fig. 2 is a control method of an electric spring system with consideration of non-critical loads according to the present invention, which mainly includes the following steps:
(1) By collecting the current i flowing through the branch of the power spring 2 Generating a synchronous phase angle through a phase-locked loop to provide a phase reference for a control circuit;
(2) The voltage sensor collects the voltage signal V of the public connecting point S Reference signal V S_ref Is subtracted to obtain an error signal e 0 Error signal e 0 Transmitting the reference signal into a proportional-integral PI controller, and performing amplitude limiting processing to obtain a reference signal V of q-axis voltage ES_q ；
(3) By detecting non-critical loads Z NCL Voltage V on NCL Judgment of the voltage V NCL Whether the maximum fluctuation range (V) of the non-critical load itself is exceeded lower ,V upper ) (ii) a Loading a non-critical load Z NCL Voltage V on NCL Upper limit of voltage V upper Lower voltage limit V lower Sending the signal into a comparator; when V is 0 Below the lower limit, V lower And V NCL Differencing to obtain an error signal e 1 (ii) a When V is NCL Above the upper limit, V upper And V NCL Differencing to obtain an error signal e 1 (ii) a If the maximum fluctuation range (V) is not exceeded lower ,V upper ) If the comparator does not operate, the error signal e is outputted 1 0, i.e. no adjustment; will error signal e 1 Transmitting the signal into a proportional integral PI controller, and performing amplitude limiting processing to obtain a reference signal V of d-axis voltage ES_d ；
(4) Will V ES_d 、V ES_q After the conversion, the output reference voltage V of the inverter is obtained after amplitude limiting treatment ES_ref ；
(5) Collecting voltage V on filter capacitor ES Will V ES_ref The difference is made to obtain an error signal and the error signal is transmitted to a proportional resonant controller to obtain the output reference voltage V of the inverter ES_out ；
(6) The reference voltage V is used ES_out The modulated wave as SPWM is compared with triangular carrier wave, and the modulated wave and carrier wave are comparedObtaining a driving signal for controlling the on-off of a switch tube in the single-phase voltage source type inverter at the intersection point moment;
fig. 3 shows a specific implementation manner of the power spring system and the control method thereof for considering non-critical loads in the present invention. When the sensor detects a voltage fluctuation on the critical load, a power spring is put in to suppress the critical load Z CL The voltage on fluctuates. When the non-critical load Z is judged NCL When the system is not connected or fails, the system operates in a non-critical load mode and only performs reactive compensation. Otherwise, while compensating for the reactive power, the non-critical load Z is detected NCL Whether the voltage on exceeds its maximum fluctuation range (V) lower ,V upper ). And if the maximum fluctuation range is exceeded, the power spring performs active compensation. When the power spring portion fails, the power spring is removed from operation. Embodied as non-critical loads Z NCL When the switch is switched on and has no fault, the switches S1 and S4 are closed, the switches S2 and S3 are opened, otherwise, the switches S1, S2, S3 and S4 are all opened.
Fig. 4 is a phasor diagram of parameters of each part of a circuit of a power spring system considering non-critical load when the non-critical load is a resistive load. It can be seen from the figure that the voltage on the non-critical load is regulated to be within the operating range thereof through active compensation while the voltage on the critical load is stabilized through reactive compensation.

Claims (4)

1. An electric spring system for non-critical loads, comprising a bi-directional DC power supply V DC The power supply type inverter comprises a single-phase controlled voltage source type inverter with two-level topology, an LC low-pass filter for filtering high-frequency components in output voltage of the inverter, a power spring, a non-critical load Z and a filter capacitor C NCL After series connection, the same key load Z CL Parallel to the point of common coupling PCC; the controller of the inverter in the power spring system detects the flow of the non-critical load Z through the current sensor NCL Current on to determine non-critical load Z NCL Access state and whether failure occurs, and control on according to state of non-critical loadAnd changing the working state of the system.
2. The power spring system for non-critical loads according to claim 1, wherein the power spring can be switched by controlling the bypass switch S1 when the switches S2 and S4 are closed and the switch S3 is open; when the non-critical load is not accessed or the non-critical load fails, the switches S1, S2 and S4 are all switched off, and the power spring is directly connected with the critical load in parallel at a common connection point PCC; when the power spring part fails, the power spring is out of operation, embodied as a non-critical load Z NCL When the switch is switched on and has no fault, the switches S1 and S4 are closed, the switches S2 and S3 are opened, otherwise, the switches S1, S2, S3 and S4 are all opened.
3. A control method of a power spring system considering non-critical loads is characterized in that reactive compensation is adopted to adjust the voltage on the critical loads to inhibit voltage fluctuation on the critical loads, and when the voltage of the non-critical loads exceeds the maximum working range of the voltage, the adjustment of the voltage on the non-critical loads is realized through active compensation to ensure that the voltage of the non-critical loads is within the maximum working range; the control method mainly comprises the following steps:
(1) By collecting the current i flowing through the branch of the power spring 2 Generating a synchronous phase angle through a phase-locked loop to provide a phase reference for a control circuit;
(2) The voltage sensor collects the voltage signal V of the common connection point S Reference signal V S_ref Is subtracted to obtain an error signal e 0 Error signal e 0 Transmitting the reference signal into a proportional-integral PI controller, and performing amplitude limiting processing to obtain a reference signal V of q-axis voltage ES_q ；
(3) By detecting non-critical loads Z NCL Voltage V on NCL Judgment of the voltage V NCL Whether the maximum fluctuation range (V) of the non-critical load itself is exceeded lower ,V upper ) (ii) a Loading a non-critical load Z NCL Voltage V above NCL Upper limit of voltage V upper Lower voltage limit V lower Sending the signal into a comparator; when in useV 0 Below the lower limit, V lower And V NCL Differencing to obtain an error signal e 1 (ii) a When V is NCL Above the upper limit, V upper And V NCL Differencing to obtain an error signal e 1 (ii) a If the maximum fluctuation range (V) is not exceeded lower ,V upper ) If the comparator does not operate, the error signal e is outputted 1 0, i.e. no correction; will error signal e 1 Transmitting the signal into a proportional integral PI controller, and performing amplitude limiting processing to obtain a reference signal V of d-axis voltage ES_d ；
(4) Will V ES_d 、V ES_q After conversion, the inverter output reference voltage V is obtained after amplitude limiting treatment ES_ref ；
(5) Collecting voltage V on filter capacitor ES A V is measured ES_ref Error signal is obtained by subtracting the reference voltage from the reference voltage and is transmitted to the proportional resonant controller to obtain the output reference voltage V of the inverter ES_out ；
(6) The reference voltage V is used ES_out The modulation wave as SPWM is compared with a triangular carrier wave, and a driving signal for controlling the on-off of a switch tube in the single-phase voltage source inverter is obtained at the intersection point moment of the modulation wave and the carrier wave;
when a non-critical load is connected and no fault occurs, the power P in the system satisfies the following formula:
Figure FDA0003919547040000011
P＝P NCL +P CL (2)
wherein Z is NCL Is a non-critical load; z CL Is a critical load; v S Being the voltage of the point of common coupling PCC, also the critical load Z CL Voltage at both ends; v ES Outputting voltage for the power spring, namely the voltage on the filter capacitor; p NCL Active power consumed for non-critical loads; p CL Active power consumed for critical loads.
4. A compromise according to claim 3Method for controlling an electric spring system for key loads, characterized in that said non-critical loads themselves have a maximum fluctuation range (V) lower ,V upper ) The default upper limit is equal to 1.2 times of the rated voltage, and the default lower limit is equal to 0.8 times of the rated voltage, and the default upper limit and the default lower limit can be changed according to actual requirements.
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CN106532716A (en) * 2016-10-28 2017-03-22 广东电网有限责任公司电力科学研究院 Intelligent load regulation circuit and control system
CN108599191A (en) * 2018-03-06 2018-09-28 东南大学 A kind of electric power spring power decoupling control method of belt current inner ring

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CN106532716A (en) * 2016-10-28 2017-03-22 广东电网有限责任公司电力科学研究院 Intelligent load regulation circuit and control system
CN108599191A (en) * 2018-03-06 2018-09-28 东南大学 A kind of electric power spring power decoupling control method of belt current inner ring

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