55 results about "Instantaneous power theory" patented technology

The invention discloses a microgrid inverter multi-loop control method based on a virtual synchronous generator, and the method comprises power control of an outer loop and voltage current control of an inner loop. The power control of the outer loop comprises the following steps: measuring the three-phase voltage and current of an output side of an inverter, calculating active power and reactive power according to the instantaneous power theory, carrying out calculation and regulation through an active power-frequency equation, a reactive frequency equation, a torque inertia equation and an electromagnetic transient equation of a synchronous motor, obtaining the amplitude of an output voltage and a phase angle given value, and then carrying out modulation through voltage and current double loops. The method can achieve the non-corresponding control of voltage size and frequency well, outputs active and reactive power, can achieve precise manual control, and has the characteristics of V/F and PQ control. When a fault happens to a power grid, the method can simulate the primary modulation, primary voltage regulation and inertia characteristics of the synchronous generator, participates in the power grid adjustment, provides frequency and voltage support, and facilitates the stabilization of the power grid.

The invention discloses a model prediction current control method based on an NPC topology grid connected inverter under asymmetric voltage, introducing the model prediction current control technology into the NPC grid connected inverter control. The model prediction current control method disclosed by the invention comprises steps of introducing decoupling double synchronization reference coordinate system phase-locked loop (DDSRF-PLL) phase lock technology to perform tracking on a positive sequence voltage phase angle in order to accurately track the positive sequence voltage phase angle under the condition that the power system has the asymmetric fault, on the basis, utilizing the DDSRF-PLL to decouple to obtain fundamental frequency voltage positive and negative sequence components, realizing a model prediction current control with the inhibition of the negative sequence current component, the active power oscillation and the reactive power oscillation as the control goal by combining with a instantaneous power theory, and adding a weight coefficient item into a cost function in order to guarantee the capacitor voltage balance on the DC side of the NPC grid connected inverter in the control process. In the whole control process, the invention reduces the usage of the PI controller, enhances the responding speed of the system, and enables the two sides of the grid connected inverter to have higher electric energy quality and stability.

The invention discloses a fault protection and ride-through control system and method for a virtual synchronous machine. The fault protection and ride-through control method for the virtual synchronous machine comprises the following steps of measuring the three-phase voltage and current on the inverter output side, and calculating the active power according to an instantaneous power theory; if an asymmetric voltage drop fault occurs, extracting the voltage positive sequence component of the power grid to obtain a switching signal, and calculating the correction amount when the active power and the reactive power need to be output; if the voltage drop depth of the power grid exceeds a preset value, obtaining a supporting voltage through a power system stabilizer; and performing calculation and regulation through an active equation, a reactive equation, a torque inertia equation, and an electromagnetic torque equation to obtain the amplitude value and the phase angle setting value of the output voltage, and performing PWM modulation. According to the fault protection and ride-through control system and method, an energy storage unit is adopted for performing voltage-stabilizing control; and the direct bus voltage is stabilized while it is ensured that overcurrent does not occur, so that huge voltage fluctuation is avoided, and the performance degradation of the system is prevented.

The invention discloses a photovoltaic grid-connected and electric energy quality management unified control strategy comprising the following steps that 1) photovoltaic component output is detected in real time, and the operation mode of a photovoltaic grid-connected system is adjusted; when the active grid-connected conditions are not met, the photovoltaic grid-connected system operates in an electric energy quality management mode, and when the active grid-connected conditions are met, the photovoltaic grid-connected system operates in an active grid-connected and electric energy quality management unified mode; and 2) when the photovoltaic grid-connected system operates in the active grid-connected and electric energy quality management unified mode, the photovoltaic grid-connected system allocates residual capacity of the photovoltaic grid-connected system according to priority of reactive power and harmonic compensation firstly and then integrates command current based on the instantaneous power theory. Compared with conventional methods, the photovoltaic grid-connected system is enabled to have a function of actively participating in power gird electric energy quality management on the basis of maintaining the original functions so that utilization rate of an inverter is enhanced, use of an electric energy quality management device is reduced and cost is saved.

The invention discloses a direct power prediction control method of a three-level grid-connected inverter model. The method comprises the following steps that 1) synthesis of three vectors is used in a three-level spatial vector modulation method, and an objective function is determined according to an instantaneous power theory and a direct power prediction control method; 2) a virtual vector is constructed, a large sector position where the virtual vector is positioned is determined, and a value of the virtual vector is calculated; 3) a small sector position where the virtual vector is positioned is determined; 4) action time of each of three vectors in the next switching period is calculated; and 5) and a switching sequence is determined according to balance of a mid-point voltage. The method is low in computational complexity, ripples of active and reactive power of the grid-connected inverter are low, the dynamic and static performances are high, and a harmonic wave inhibition effect is good.

The invention discloses a control method for high-power reactive and harmonic dynamic hybrid compensation method. The hybrid compensation system comprises an SVG (static var generator), a TSF (thyristor switched filter) group and a controller, and the SVG and TSFs are parallelly connected to a grid. The three-phase current of the grid between the SVG and the TSFs is taken as a detection object, voltage and current values collected by sensors are processed through the controller, switching signals of the TSFs are acquired according to hybrid logic judgment, most of the reactive power of loads is compensated in a graded manner, and specific subharmonic is filtered out; control parameters of the SVG are acquired according to an instantaneous-power theory, and the surplus reactive power and harmonic of the loads are continuously compensated. A cost-effective scheme for rapid continuous compensation of the high-power reactive and harmonic is provided, impact of switching of passive equipment on the grid can be completely avoided, and harmonic current is avoided flowing to the grid, so that the control method is energy saving, emission reducing, green, environment friendly, good in social and economical effectiveness, wide in application range and especially applicable to the field of oil drilling.

The invention discloses a method for controlling output current peak values of a photovoltaic inverter during temporary asymmetric voltage drop, and belongs to the field of photovoltaic power generation control technology. The method comprises the steps of calculating the reference value of the output current of the photovoltaic inverter under the condition of temporary asymmetric voltage drop on the basis of an instantaneous power theory; calculating the output current peak values of the photovoltaic inverter and the possible maximum current peak value; putting forward the restrictive measures for the output current peak values according to a current peak value expression; designing an output current control structure of the photovoltaic inverter under the condition of the temporary asymmetric voltage drop. The method for controlling the output current peak values of the photovoltaic inverter during the temporary asymmetric voltage drop has the advantages that grid connection current control of the photovoltaic inverter during the temporary asymmetric voltage drop can be achieved effectively, the fact that the output currents of the photovoltaic inverter under the condition of the temporary asymmetric voltage drop cannot exceed the maximum current limiting value is guaranteed, and therefore the potential safety hazards brought to operation of a photovoltaic system by enlargement of the current peak values are eliminated.

The invention discloses a fractional calculus-based PWM rectifier modeling method, and according to the method, a precise mathematic model of a single-phase PWM rectifier can be established on the basis of a fractional calculus theory and an instantaneous power theory defined by Caputo. The method comprises the following steps: firstly determining a voltage equation and a current equation of the single-phase PWM rectifier in a rest frame; defining and establishing a fractional order inductance equation and a fractional order capacitance equation of the single-phase PWM rectifier, and giving an input instantaneous power equation and an output instantaneous power equation of the single-phase PWM rectifier; and finally giving a direct-current component equation and an alternating-current component equation in an input instantaneous power and an output instantaneous power, and verifying the precision of the fractional calculus-based single-phase PWM rectifier fractional order model established on the basis of numerical simulation. According to the method, the fact that the capacitance and inductance are fractional orders in essence is considered in the modeling process, so that the modeling precision of the single-phase PWM rectifier.

The invention discloses a current mode inverting control strategy for inhibiting current harmonic waves and three phase imbalance in a micro grid. The current mode inverting control strategy for inhibiting the current harmonic waves and the three phase imbalance in the micro grid includes: superposing d axis and positive sequence voltage of a load for Park transformation based on a traditional instant power theory so as to measure a harmonic current of the load; obtaining fundamental voltage of the load and fundamental voltage of a micro source inverter output port, which are equal to each other due to the fact that load is connected with a micro source side in parallel; accordingly, adding a micro source power control link based on harmonic detection control, and enabling a detected current signal to contain a power current signal output by a micro source; enabling an inverter output current to track the current signal through current hysteresis control, and thereby meeting output requirements of the micro source, and managing power quality problems in the micro grid.

The invention discloses a method for additional function control for a modularized multilevel current converter. The method comprises the steps that alternating voltages and alternating currents at the load side are collected; based on the instantaneous power theory, a harmonic current instantaneous value at the load side is calculated; a harmonic current instantaneous calculation value is adjusted by a closed loop so that an additional control voltage order can be obtained; the additional control voltage order and the power control voltage order are added together to serve as a voltage control order of the modularized multilevel current converter; alternating voltages and alternating currents at the load side are collected again. Under the condition that a filter device is not additionally arranged, harmonic pollution, caused by a harmonic source, of a connected alternating current system is effectively reduced, the power grid power quality is improved, and the stability and the quality of the system are improved.

The invention relates to an integrated flexible arc extinguishing method of a single-phase grounding fault of a power distribution network. Multiple functions of arc extinguishing of the single-phasegrounding fault of the power distribution network, active power and reactive power control of a load and the like are realized by using multi-level converter integration. Independent control of activepower, reactive power and zero-sequence power is achieved through current decoupling control under a rotating coordinate system. The control of the active power and the reactive power of the load isrealized by utilizing an instantaneous power theory, and the control of zero-sequence power is realized by a flexible arc extinguishing algorithm of the single-phase grounding fault. For problems thatan existing active arc extinguishing device is single in function; and cost performance is low due to high cost, in the invention, the same set of power electronic equipment has the multiple functions of active power control, reactive power control, single-phase grounding fault arc extinguishing and the like, utilization efficiency of the power electronic equipment is greatly improved, capacity expansion is easy, and dispersion localization of grounding fault arc extinguishing and reactive power compensation can be realized.

The invention discloses an on-line diagnosis method for a turn-to-turn short circuit fault of a non-electromagnetic coupling low-thermal coupling double redundancy permanent magnet synchronous motor coil among each winding based on an instantaneous power principle. When a coil turn-to-turn short circuit of a certain set of three-phase winding occurs, corresponding equivalent resistance, equivalentinductance and equivalent induction electromotive force of the phase where the fault coil is located change, fault winding parameters are differed from normal three-phase winding parameters when 3/2static coordinate system switching is conducted, currents of the two three-phase winding are almost the same, and therefore the situation where instantaneous active power or instantaneous reactive power is consumed by the fault three-phase winding is differed from the normal three-phase winding. According to the method, the motor is in a braking state or an electric state, the absolute value and the average value of the difference of the instantaneous active power or the difference of the instantaneous reactive power of the two windings, whether the absolute value or the average value is positive or negative and the forward or reverse rotation state of a motor within the latest limited sampling control periods are calculated in real time to judge coil turn-to-turn short circuit fault occurs on which three-phase winding on line.

The invention discloses a PWM rectifier model prediction method and device based on fixed vector synthesis. According to a mathematical model and an instantaneous power theory of a rectifier, complex power Sk at the k moment, a complex power prediction value Sk+1 at the k+1 moment and a complex power reference value Sref are solved; according to the complex power prediction value Sk+1 and the complex power reference value Sref, a reference voltage vector vref is obtained; according to the reference voltage vector vref, SVPWM duty cycle information is obtained through prediction and control of a PWM rectifier model using fixed vector synthesis, and action time tx of a non-zero vector Vx and action time t0'' of a zero vector V0' of a double-vector method are obtained; according to the action time tx of the non-zero vector Vx and the action time t0'' of the zero vector V0', a drive signal of each switch tube of the whole rectifier is constructed. Thus, the method and device do not need a lot of enumeration calculation processes, is based on fixed vector synthesis SVPWM and has the function of freely switching between SVPWM and double vectors.

The invention relates to a voltage source-type energy storage micro grid power quality improvement predictive control method. The energy storage system serves as an important part of the micro grid, and research on multiple usages of the energy storage system in the micro grid plays an important role in improving the utilization efficiency. On the basis of analyzing the feasibility of using voltage source-type energy storage to realize harmonic current compensation, a multiple predictive control method of improving micro grid voltage and frequency dynamic stability and compensating the harmonic current by the energy storage system is researched. Firstly, based on an ip-iq detection method for the harmonic current and an instantaneous power theory and in combination with a GM (1,1) gray model, a comprehensive instruction current compensation predictive method for multifunctional control of the energy storage device is researched and realized; then, based on a dynamic model for voltage source-type converter output current, through building an optimal switch selection function for the converter, a predictive control strategy for tracking the comprehensive instruction current based on the optimal switch mode is provided for an energy storage system grid-connected converter; and finally, effectiveness of the provided switch control strategy is verified.

The invention relates to a direct power boundary control method based on a three-phase three-throw two-level rectifier. A mathematical model of the three-phase three-throw two-level rectifier in a two-phase synchronous rotating coordinate system is established; a power model of the rectifier in the rotating coordinate system is established by combining an instantaneous power theory and a voltage orientation principle; a standard phase plane is established by taking the DC side voltage as the transverse axis and the AC side current as the longitudinal axis, and change of a natural trajectory ofthe rectifier when the AC-side current of the rectifier is decreased and increased in the standard phase plane is analyzed; and on the basis of the power amount, a boundary control condition is usedto crease novel direct power control, a natural switching side of boundary control is selected by taking the natural trajectory of the rectification system, when the AC-side current is decreased and increased, as basis, the natural switching side is used to update output rule of direct power control in a power hysteresis comparator, and finally a direct power boundary control method is obtained. The dynamic performance in the DC side of the three-phase three-throw two-level rectifier can be improved effectively aimed at the abrupt load change in practical application.

The invention discloses a zero-dynamic DC output voltage control method and system of a current source converter. According to the invention, a power grid voltage feedforward control item and a DC side output current feedforward control item are effectively calculated through the instantaneous power theory, the small signal model analysis, the superposition theorem and other methods; the zero-dynamic DC output voltage control method of the current source converter is provided on such basis, and by adopting the DC output voltage and power grid voltage feedforward control technology, the methodcan realize stable DC output voltage, and can realize zero-dynamic adjustment of the output voltage under the condition that the power grid voltage fluctuates; furthermore, no matter under the condition of balanced drop or unbalanced drop of the power grid voltage, zero dynamic adjustment of the DC output voltage can be realized by adopting the method, the power supply quality of the current source converter is effectively improved, and the method is simple in implementation process and has a great practical engineering application value.

The invention discloses a control method with fault diagnosis and automatic restoration functions for a hybrid compensation system. According to the control method for the hybrid compensation system, power grid three-phase currents between an SVG and a TSF group as well as output three-phase currents of the TSF group are regarded as detection objects, voltage and current values acquired by sensors are processed through a controller, the TSFs are controlled to compensate most of reactive power of a load in a graded manner and filter out specific subharmonic waves by using a diagnostic control module, when one of the TSFs fails, the faulty TSF is diagnosed and cut off automatically, and the normal TSFs are reconfigured on demand and put into service, so that the hybrid compensation system has the automatic restoration function; in addition, control parameters of the SVG are obtained according to an instantaneous power theory, so as to achieve continuous compensation of residual reactive power and harmonic waves of the load. The control method ensures stable and reliable operation of the hybrid compensation system in normal and fault states of the TSFs, greatly increases system operating efficiency, and reduces system later-stage maintenance cost. The control method for the hybrid compensation system saves energy, reduces emission, is green and environmentally friendly, has good social and economic benefits, and is particularly suitable to be used in the petroleum drilling field with high damage rate of the TSF due to harsh environment.

The invention relates to a current limiting method suitable for a grounding fault in an AC microgrid. The method comprises the following steps of S1, improving the design of optimal parameters of droop control, constructing a Bode diagram according to a droop control transfer function equation containing a washout filter, and selecting optimal parameters through simulation comparison; S2, an instantaneous power theory being improved, specifically, based on the fact that a traditional instantaneous power theory is only suitable for a single-phase earth fault, the instantaneous power theory containing a double rated current amplitude limiting link being constructed, wherein the instantaneous power theory can be suitable for a two-phase earth fault and a three-phase earth fault; S3, voltage and current double-loop control, utilizing the static error-free tracking performance of a quasi-PR controller, and utilizing quasi-PR control to realize accurate tracking of reference voltage by an outer loop; aiming at a problem that traditional passive control is greatly influenced by parameter disturbance, an inner loop adopts improved passive control to realize accurate tracking of filter inductance current, and voltage and current control is carried out on a converter in a microgrid in combination with an SPWM modulation algorithm. Compared with the prior art, the method has the advantages of being good in fault current asymmetry degree, high in fault recovery speed and the like.

The invention provides an MMC alternating-current side near-end asymmetric fault short-circuit current calculation method. The method comprises the steps that alternating-current voltage and current at a PCC are decomposed into positive-sequence dq-axis components and negative-sequence dq-axis components through a phase sequence separation module; calculating real-time active power and reactive power transmitted by the MMC when an asymmetric fault occurs according to an instantaneous power theory; judging the type of a power outer loop controller, calculating a positive sequence dq-axis current instruction value, and converting the positive sequence dq-axis current instruction value into a positive sequence dq-axis current instruction value and a negative sequence dq-axis current instruction value; according to the MMC mathematical model of the positive and negative sequence dq-axis components and the mathematical model of the positive and negative sequence decoupling inner loop current controller, solving a transfer function of the positive and negative sequence current output by the MMC and the instruction value of the positive and negative sequence dq-axis current; and calculating the short-circuit current fed into the short-circuit point by the MMC according to the positive and negative sequence current. According to the method, reference is provided for MMC controller parameter setting and alternating current system relay protection parameter setting, and the method can be used for analyzing the active power and reactive power characteristics of MMC transmission after an asymmetric fault occurs on the near-end alternating current side of the MMC.

The invention discloses a comprehensive control method for power fluctuation stabilization and electric energy quality treatment of a micro-grid based on an energy storage converter, and the method comprises the steps: firstly, calculating the power of a grid-connected point based on an instantaneous power theory according to two output modes of power fluctuation stabilization and electric energy quality treatment of the energy storage converter; a main and auxiliary mode switching control strategy of the energy storage converter is determined by comparing the power required by the local load and the energy storage residual power; in order to prolong the service life of the energy storage system, an energy storage capacity distribution strategy based on reactive power/harmonic wave/three-phase imbalance priority is also provided, compensation priorities are set for three electric energy quality problems existing in the micro-grid, and the electric energy quality problem with a higher compensation level is preferentially compensated according to the residual capacity of the energy storage system. According to the invention, an energy storage converter main and auxiliary mode switching control strategy and a reactive/harmonic/three-phase unbalanced priority energy storage capacity distribution strategy are effectively combined, the problems of grid connection and electric energy quality of a micro-grid are greatly improved, and the operation economy of an energy storage battery is improved.

The invention relates to a three-phase unbalanced load current active compensation control method, and belongs to the field of electric energy treatment. Instantaneous power is improved according to abasic structure and a working principle of the two-level SVG, and current is decomposed to a synchronous rotating coordinate system instead of directly decomposing the power according to a traditional instantaneous power theory. Aiming at the extraction of instruction current, a software phase-locked loop phase-locked method based on a single synchronous coordinate system is adopted, an SPLL linearized model is obtained based on a dq coordinate transformation principle, and a novel three-phase SPLL is realized through PI control. For a current control algorithm, a current control method basedon model predictive control is adopted. The three-phase unbalanced circuit can be compensated in real time, and can be conveniently applied to an actual power system. The method is flexible, simple and high in accuracy. The method has the advantages of being scientific, reasonable, high in applicability, high in reliability and good in effect.