39results about How to "Does not affect power quality" patented technology

The invention discloses a rapid detection island method of a distributed grid-connected generation system. A power grid, a circuit breaker, a transformer, a gird-connected inverter and a local load are included. The power grid is connected in series with the circuit breaker through an electric wire and one side of the circuit breaker is connected in series with the transformer. The transformer is connected to the gird-connected inverter and the local load. The local load is arranged on one side of the gird-connected inverter. When a photovoltaic system operates normally, a reactive power disturbance mode is set and a modulation wave commutation period is detected and output. If a rate of change of the commutation period exceeds a threshold value, it is possible to generate an island in the power grid, at this time, the system memorizes a current voltage amplitude and a frequency and simultaneously the set is changed into an active disturbance mode. A photovoltaic system MPP point is actively deviated so that the system does not match with load power. Through comparing the voltage amplitudes and the frequencies memorized by the system, whether the island is generated is determined. By using the island detection method, when the island is generated, rapidity and accuracy of detection are increased.

The invention discloses a grid-connected inverter island detection method based on wavelet transform and a neural network. The method is characterized in that the method comprises the following steps: firstly, gathering voltage values of a distributed grid-connected power generation system at a point of common coupling at island state and non-island state and the output current value of an inverter, then performing wavelet transform on the gathered voltage values and the output current value of the inverter and exacting high-frequency component wavelet coefficients to be processed, and finally taking processed signals as input signals of the neural network, and taking corresponding island state and non-island stage as output signals to train the neural network, so as to ensure that the system obtains recognition capability to the island state and the non-island state, and to adopt corresponding island protection measures when the distributed grid-connected power generation system is at the island state. The method can not only overcome the disadvantages of the existing passive island detection method that the detection blind area is large and the detection time is long, but also can solve the problem that the active island detection method affects the power supply quality of the distributed grid-connected power generation system, and rapidly accomplish island detection and island protection.

The invention discloses a photovoltaic auxiliary commercial power AC power supply system comprising a solar cell boosting module which provides high voltage DC, a high voltage DC / AC inversion module which converts the high voltage DC and outputs photovoltaic power supply AC having the same frequency and the same phase with those of commercial power, and a power supply module which performs AC isolation and line combination on the commercial power and the photovoltaic power supply AC and the supplies power to a load. The AC isolation and line combination power supply module comprises a one-way coupling isolation control circuit which is connected with the commercial power and provides commercial power AC to the load at the output end. The photovoltaic power supply AC and the output end of the one-way coupling isolation control circuit are connected in parallel and then supply power to the load together. The one-way coupling isolation control circuit only allows passing of the commercial power and prevents the photovoltaic power supply AC from feeding into the commercial power grid. The photovoltaic auxiliary commercial power AC power supply system is simple and reasonable in structure, low in manufacturing cost without storage battery and pollution-free to the environment so that the reactive current of the load can be prevented from entering the commercial power grid.

The invention discloses a power sharing control method for an open winding twin inverter photovoltaic power generation system. In allusion to the problem of uneven power distribution of two inverterscaused by adopting a decoupling modulation strategy of 120-degree mutual difference in a common direct current bus open winding twin inverter photovoltaic power generation system, the invention bringsforward a power sharing control method based on reactive power compensation. According to the method, the reactive current command value of the two inverters is obtained by adjusting the active powerdifference of the two inverters, thus realizing the power sharing of the two inverters. Compared with an existing method, the invention has the following beneficial effects: the power quality of grid-connected current is not affected while realizing the control target, and the control method is simple and easy for engineering implementation.

The invention discloses a method for islanding detection based on harmonic impedance characteristic function pattern recognition and relates to the technical field of electrical property testing methods. The method comprises a step (1) of collecting voltage at a public coupling point and an access current of a distributed type grid-connected power generation system when the distributed type grid-connected power generation system is in an islanding state and a non-islanding state; a step (2) of establishing a harmonic impedance characteristic function phi(k) according to a voltage value and a current value collected in the step (1), and obtaining a characteristic vector space; a step (3) of performing training on a learning sample through pattern recognition, and obtaining the distinguishing capability of the distributed type grid-connected power generation system in the islanding state and the non-islanding state. According to the method, on the premise that electric energy quality is not affected, islanding is accurately detected and islanding protection is performed so as to reduce or even eliminate an islanding detection blind area.

The invention discloses a modular multilevel converter type high-voltage direct-current power transmission (MMC-HVDC) project. After the project is accessed to an alternating-current power grid, a negative sequence direction relay on a power transmission line cannot correctly judge a fault direction and cannot correctly act. In order to solve problems, the invention discloses an MMC-HVDC control strategy assisting in fault direction discrimination. The strategy can assist the negative sequence direction relay to correctly and sensitively identify the fault direction on the basis of basically not influencing safe operation of the MMC, ensures the correct action of the relay, and ensures safety of operation of a power grid.

The invention discloses a multifunctional off-grid type charging pile using methanol as fuel. The multifunctional off-grid type charging pile comprises a whole vehicle control system, a motor control system, an intelligent electric distribution system, an electric vehicle motor, a battery managing system, a fuel supply system, a fuel battery system, an intelligent charging pile, an emergency electric source system, and a power battery system, wherein the whole vehicle control system is connected with the motor control system, the battery managing system, the fuel battery system and the power battery system; the motor control system is connected with the intelligent electric distribution system and the electric vehicle motor; the intelligent electric distribution system is connected with the battery managing system, the fuel battery system, the intelligent charging pile, the emergency electric source system and the power battery system. According to the multifunctional off-grid type charging pile using methanol as fuel disclosed by the invention, alcohol hydrogen fuel which is free from pollution is used for solving the problems of the endurance of an electric vehicle, the charging of the electric vehicle and the electric supply of a communication base station, and the multifunctional off-grid type charging pile has the characteristics of being convenient to operate, short in starting time, long in charging time, low in occupied space, light in weight, low in noise, free from pollution and the like.

The invention relates to an intelligent high-precision voltage stabilizer with self-adaptive wide dynamic power supply. The main loop of the intelligent high-precision voltage stabilizer comprises one compensation transformer, 4 IGBTs (Insulated Gate Bipolar Translators) and an intelligent driving control system; the four IGBTs under the control of input power live wires and chopped waves are connected with a harmonic suppression inductor L1; a first contact (KM1) head and a second contact (KM2) head are connected with the tail end of a primary side of the compensation transformer (T1); and a third contact (KM3) head is connected in parallel with the first end and the tail end of a secondary side of the compensation transformer (T1). As a voltage value is adjusted and compensated by using a chopped wave control technique, wide dynamic power supply and high-precision voltage output are achieved.

The invention discloses a power equal sharing control method of an open-winding dual-inverter photovoltaic power generation system. Aiming at the problem of uneven power distribution between the two inverters caused by the 120-degree decoupling modulation strategy of the common DC bus open-winding dual-inverter photovoltaic power generation system, the present invention proposes a power equalization based on reactive power compensation A control method, the method obtains the reactive current command value of the inverters by adjusting the active power difference between the two inverters, so as to realize the equal power sharing of the two inverters. Compared with the existing method, the present invention does not affect the power quality of grid-connected current while realizing the control target, and the control method is simple and easy for engineering realization.

The invention discloses an islanding detection system and method for an inverter power source. The method mainly comprises the steps that first voltage and first currents output by the inverter power source are determined; according to the first voltage and the first currents, a control mode and an on-off control signal corresponding to the control mode are determined; a VSC main circuit determines the on-off state of the main circuit according to the on-off control signal and outputs the electricity quantity corresponding to the control mode, and the electricity quantity comprises the voltage and the currents; an islanding protecting device obtains output currents and output voltage and then judges whether the inverter power source is in an islanding state. According to the method, the first voltage and the first currents are processed in a series mode to determine the control mode of the inverter power source, whether the inverter power source is in the islanding state is judged by judging the voltage and the currents output to the main circuit and a second bus under the current control mode, detection blind areas are avoided, the voltage and the currents output by the inverter power source are adjusted through different control modes, and therefore the electric energy quality is not influenced.

The invention discloses an island detection method based on harmonic distortion rate and frequency. The method herein includes the following steps: based on historical data, determining the maximum value (H<1>) of the harmonic distortion rate when a distributive photovoltaic power generation system joints a power grid and the minimum value (H<2>) of the harmonic distortion rate when the distributive photovoltaic power generation system is an island, if (H<1> is greater than H<2>) or the values of H<1> and H<2> can not be determined, and after it is detected that the harmonic distortion rate suddenly increases and lasts for a while, starting the harmonic distortion rate criterion and frequency varying amount to determine an island state; if (H<1> is smaller than H<2>), directly starting the harmonic distortion rate criterion and frequency varying amount to determine an island state. According to the invention, the method herein does not add a disturbing signal to the distributive photovoltaic power generation system, does not affect the quality of the electric energy of the distributive photovoltaic power generation system, and does not cause damage; uses the harmonic distortion rate and frequency, has small detection blind areas, increases the reliability of system island detection; and avoid sudden disturbance in the power grid by using a certain time delay, and prevents temporary change to the detected electric quantity from causing wrong determination of island detection.

The invention provides a V2G direct current charging and discharging facility inspection device and a discharging method, at least one V2G charger is installed on the basis of a single electric vehicle charging station, and the V2G direct current charging and discharging facility inspection device at least comprises a control module, a battery voltage module and a relay contactor; the battery voltage module is used for simulating power supply voltage output of a battery in the starting process of the charger; the relay contactor is used for controlling on and off of each switch; and the control module is used for switching and protocol control of communication ports between equipment connected with the charging input interface and equipment connected with the charging output interface, and discharging control of an internal small cycle formed by the power grid, the charger, the V2G charging and discharging facility inspection device, the V2G charger and the power grid in sequence.

The invention provides a method for distinguishing an island phenomenon from a grid-side voltage transient disturbance phenomenon. The method is suitable for a photovoltaic grid-connected system faultdetection technology. According to the method, change characteristics of a harmonic voltage before and after different faults are taken as a main basis, and the influence of main power grid background harmonic and spectrum leakage on harmonic detection is comprehensively considered. According to the method, a harmonic voltage threshold setting formula is specifically provided, the island phenomenon and the voltage transient disturbance phenomenon can be effectively distinguished, interference of frequency spectrum leakage and the main power grid background harmonic is avoided, and the methodhas practical feasibility.

A micro-grid system with micro-source half-bridge converters in series, including photovoltaic micro-sources, wind micro-sources, energy storage devices, AC / DC rectifier circuits, DC / DC conversion circuits, micro-source half-bridge converters, filtering The inverter, load, transformer, wind power and photovoltaic micro-source are connected in parallel to the DC side of the micro-source half-bridge converter through the AC / DC rectifier circuit or DC / DC conversion circuit, and the energy storage device is connected in parallel to the micro-source DC link. , the output side of each micro-source half-bridge converter is sequentially connected in series, and a three-phase system is built by a double-star combination, in which each phase is composed of two bridge arms, and each bridge arm is composed of N One or n power generating sub-modules are connected in series with an inductor, 2≤N≤50, N=n.

The invention relates to a substation area control method and system of a microgrid operation mode. The substation area control method comprises the following steps of: when a power generation system is subjected to grid-connected power generation according to a first operation mode, if an island operation state appears and a grid-connected power generation mode exits, judging whether the low voltage side of a transformer for a substation corresponding to a second operation mode of the power generation system has voltage, judging which state automatic throw-in equipment of emergency power supply is; if the low voltage side has voltage and is in a commissioning state, receiving correct action formation of the automatic throw-in equipment of emergency power supply and starting the second operation mode; and if the low voltage side does not have voltage or the automatic throw-in equipment of emergency power supply is in an exit state, or the correct action information of the automatic throw-in equipment of emergency power supply is not received within preset time, locking the automatic throw-in equipment of emergency power supply and then starting the microgrid operation mode. According to the substation area control method and system, concentrated judgment and computation are carried out by acquiring real-time operation information of parts in the substation transformer area, which are related to the power generation system, and effective control based on the substation-grid microgrid operation mode is achieved.

The invention discloses a rapid detection island method of a distributed grid-connected generation system. A power grid, a circuit breaker, a transformer, a gird-connected inverter and a local load are included. The power grid is connected in series with the circuit breaker through an electric wire and one side of the circuit breaker is connected in series with the transformer. The transformer is connected to the gird-connected inverter and the local load. The local load is arranged on one side of the gird-connected inverter. When a photovoltaic system operates normally, a reactive power disturbance mode is set and a modulation wave commutation period is detected and output. If a rate of change of the commutation period exceeds a threshold value, it is possible to generate an island in the power grid, at this time, the system memorizes a current voltage amplitude and a frequency and simultaneously the set is changed into an active disturbance mode. A photovoltaic system MPP point is actively deviated so that the system does not match with load power. Through comparing the voltage amplitudes and the frequencies memorized by the system, whether the island is generated is determined. By using the island detection method, when the island is generated, rapidity and accuracy of detection are increased.

The invention discloses an energy storage converter non-communication line parallel strategy based on bus voltage event detection. The control strategy is based on the background that the load end of the energy storage converter is close, and obtains the voltage signal of the common end of the PCC point as a common event. Signal, based on the PCC voltage feedback method to realize the power sharing of each energy storage converter, based on the principle of event detection mechanism, use the event signal of PCC voltage as the synchronization signal for each energy storage converter to achieve voltage frequency recovery, thus The requirement for communication interconnection lines between the energy storage converters is avoided. The strategy control method is simple and practical, easy to improve, and has good system scalability. The construction cost of a multi-machine parallel system without interconnection lines is low, and it has relatively practical engineering application value.

The invention discloses an island detection method based on multi-frequency-band harmonic voltage and frequency, and belongs to the technical field of photovoltaic power generation systems. An islandis determined when an action condition is satisfied since a harmonic voltage rises and the frequency is deviated at a certain degree after the island. Through adoption of the island detection method,misjudgment can be avoided. Moreover, the harmonic voltage is considered, so that wrong frequency judgment is prevented, and a relatively small frequency action threshold can be set. Thus, the sensitivity is increased; the detection blind zone is reduced; and the problems in independent use of over / under-frequency detection and harmonic detection methods are solved.

The invention discloses a regenerated energy storage system with a diesel generator set as a power source. The regenerated energy storage system comprises a diesel engine set, a driving circuit, an energy storage unit and a control unit. The control unit comprises an IGBT electrical energy conversion device. The energy storage unit is a lithium battery pack or a super-capacitor set. According to the regeneration energy storage system with the diesel generator set as the power source, regenerated electrical energy in an electric control system can be recycled while alternating-current variable frequency control of lifting machinery is achieved.

The invention discloses a railway traction power supply and transformation compensation circuit based on a T-structure double-inductance branch, which relates to the technical field of electrified railway power supply and transformation engineering. The railway traction power supply and transformation compensation circuit comprises a Y-shaped three-phase primary winding, a triangular secondary winding and a V-shaped secondary winding, wherein the triangular secondary winding outputs a first phase voltage, the V-shaped secondary winding outputs a second phase voltage, and two leading-out ends of the triangular secondary winding and two leading-out ends of the V-shaped secondary winding are connected through a common connecting wire to form a T-shaped structure. The three-phase current symmetry of the primary side can be ensured by controlling the two-phase current symmetry of the secondary side, so that the three-phase unbalance degree is effectively reduced, and the influence of the access of a traction load on the negative sequence of a power grid is inhibited.

The invention relates to a control method and a control device for accessing an energy-storage photovoltaic system into an urban rail traction network, wherein the method comprises the following steps that: 1) whether a photovoltaic battery has energy output or not is judged; if so, the photovoltaic battery has the energy output, a first direct current / direct current (DC / DC) converter and a second DC / DC converter connected with the photovoltaic battery are turned on, the photovoltaic battery starts to work, and then, the operation returns to step 2); if the judgment result shows that the photovoltaic battery does not have the energy output, the photovoltaic battery does not have energy to output, the first DC / DC converter and a second DC / DC converter connected with the photovoltaic battery are turned off, the operation returns to the step 1), whether the photovoltaic battery has the energy output or not is continuously judged, after the operation is repeated for n times, the photovoltaic battery stops working, and the operation returns to the step 2) and other steps. The device comprises the photovoltaic battery, the first DC / DC converter, the second DC / DC converter, a bidirectional DC / DC converter and energy storage equipment. Compared with the prior art, the control method and the control device have the advantages that the energy loss is low, the work efficiency is high, the stability is high, and the like.

A power supply isolated wireless audio receiving device, comprising a DC input connector, a power supply isolation circuit, an audio receiving circuit and an audio output connector, wherein the DC input connector is used to receive the first DC power input from an external power supply; the power supply isolation circuit is used to connect the first The direct current is inverted and rectified into the second direct current and the ground terminals of the first direct current and the second direct current are isolated; the audio receiving circuit is electrically connected with the power supply isolation circuit and connected to the second direct current for wirelessly receiving the sound signal and converting it into Analog audio signal; the audio output connector is used to output the analog audio signal to the external device for sound playback. Since the power supply isolation circuit is set between the DC input connector and the audio receiving circuit, the first DC power input from the external power supply can eliminate the high-frequency interference signal superimposed on itself during the process of inversion and rectification, and avoid high-frequency interference signals. It is transmitted to the audio receiving circuit through a common ground.

The invention discloses a method for remotely and automatically collecting parameters of a ship's power system. Firstly, the current operating parameters of electrical equipment are sampled and held, discretized, encoded, and modulated through a collector to form a high-frequency carrier signal through a coupling circuit of the collector. Coupled into the lighting grid cable, it is transmitted to the concentrator through the lighting cable. The concentrator filters the high-frequency carrier signal from the lighting grid cable, demodulates and decodes it, and obtains the current operating parameters of the electrical equipment. The coupling circuit in the collector of the present invention is conjugate-matched to the lighting cable of the ship, which can realize the maximum transmission power of the carrier signal. The filter circuit in the concentrator matches the lighting cable of the ship without reflection, and the high-frequency carrier signal filtered out is Interferenced by reflected waves, the noise of the ship's lighting grid within the communication frequency band is small, and it has a better communication signal-to-noise ratio.