16 results about "Instantaneous power theory" patented technology

The invention discloses a DC suppression method and system for an isolated DC-DC resonant converter for energy storage, and aims to optimize voltage ripples of a resonant network. A voltage ripple mathematical model of a resonant network is constructed by using an instantaneous power theory, instantaneous power of a resonant inductor and a resonant capacitor is calculated, and three working conditions that the switching frequency of the resonant converter is equal to the resonant frequency, near the resonant frequency and far away from the resonant frequency are monitored. The range limitation of the switching frequency is determined according to a corresponding method when the resonant converter is in a corresponding working condition, so that the switching frequency of the resonant converter is dynamically adjusted along with different working conditions, output direct current ripples are effectively suppressed, and the reliability of an electric energy quality assurance system is improved.

The application discloses a double closed loop control of a reactive power compensator based on a phase quantity synthesis principle of double rotating phase shifters, and the double closed loop control is characterized in that: by measuring a voltage of a reactive power compensator access point, a load current, an inductance current and a total current of a primary side of two rotating phase shifters, the total current is converted to a dq0 coordinate system, and instantaneous power of a line is calculated by using an instantaneous power theory; reactive power of the load is taken as a feedback value, and an expected value of power closed loop control is determined by combining a power factor preset value of a power grid, the expected value and the given value are compared to form a given value of the reactive current; d and q axis components of the instantaneous current are taken as feedback values, and the closed loop control quantity is formed by comparing the d and q axis components with the given value; by using a rotating vector synthesis principle, a rotor mechanical angle instruction of each rotating phase shifter is obtained, the rotor mechanical angle instruction is adjusted through a servo controller, and then the reactive power absorbed or emitted by the reactive power compensator is changed; and the application provides a new reactive power compensation control scheme which is low in cost, strong in impact resistance, high in reliability, convenient in maintenance, omni-directional in compensation and continuous in adjustment.

The application provides a kind of voltage source converter intermediate DC voltage control method, it relates to power electronics field, the method includes: real-time detection of the electric quantity parameter of converter, electric quantity parameter includes input voltage, output voltage and output current;According to the electric quantity parameter, the feedforward additional amount of load power and the current reference value of inner loop control is calculated by virtual three-phase method and instantaneous power theory;According to the electric quantity parameter, the real-time current change rate is calculated, and the output current change rate reference value is obtained by load power calculation;The current change rate reference value and real-time current change rate are compared, and according to the comparison result, it is determined that load step occurs.The application switches the feedforward and feedback control strategy dynamically, significantly improves the DC voltage dynamic response speed and steady-state accuracy of voltage source converter when load mutates, realizes the effect of quickly suppressing voltage fluctuation and automatically recovering steady-state control.

The invention discloses a grid-connected inverter electric energy quality optimization control method for power grid voltage sag, which comprises the following steps: performing parameter preprocessing on a pre-established mathematical model of a grid-connected inverter to obtain preprocessing parameters under a two-phase static coordinate system; calculating a positive sequence voltage component and a negative sequence voltage component, and calculating an initial current reference instruction under various electric energy quality optimization modes according to an instantaneous power theory; performing dynamic correction and amplitude limiting on the initial current reference instruction based on the voltage drop depth and the low voltage ride through requirement, and generating a final current reference instruction for model prediction control; predicting a system state of a next sampling period based on the mathematical model and the preprocessing parameters, and constructing a value function by taking tracking of a final current reference instruction as a control target based on the system state; and solving an optimal inverter valve side voltage control quantity through the value function, and applying the control quantity to space vector modulation so as to drive the grid-connected inverter.

The invention provides a voltage source converter intermediate DC voltage control method, and relates to the technical field of power electronics, the method comprises the following steps: detecting electric quantity parameters of a converter in real time, the electric quantity parameters comprising an input voltage, an output voltage and an output current; according to the electric quantity parameters, through a virtual three-phase method and an instantaneous power theory, load power and a feedforward additional quantity of a current reference value of inner loop control are calculated; calculating a real-time current change rate according to the electric quantity parameters, and calculating an output current change rate reference value through load power; and comparing the current change rate reference value with the real-time current change rate, and judging that the load step occurs according to a comparison result. By dynamically switching the feedforward and feedback control strategies, the direct-current voltage dynamic response speed and steady-state precision of the voltage source converter when the load is suddenly changed are remarkably improved, and the effects of rapidly suppressing voltage fluctuation and automatically recovering steady-state control are achieved.

The application relates to a permanent magnet synchronous generator power generation voltage stabilization control strategy considering high-resistance contact faults, and steps are as follows: based on a dq rotating coordinate system, a permanent magnet synchronous generator mathematical model considering high-resistance contact faults is established; combined with the permanent magnet synchronous generator mathematical model considering high-resistance contact faults, an instantaneous power equation considering high-resistance contact faults is derived based on instantaneous power theory; combined with the instantaneous power equation considering high-resistance contact faults, a quantitative relationship between a direct-current terminal voltage double-frequency ripple and a cross-axis current is derived based on a small signal analysis method; combined with the quantitative relationship between the direct-current terminal voltage double-frequency ripple and the cross-axis current, a cross-axis current integral average compensation method is designed by taking the characteristic that a sine signal is integrated to zero in an integral period, and a compensated current is obtained to perform permanent magnet synchronous generator power generation voltage stabilization control. The application can inhibit the double-frequency ripple of the cross-axis current, and further reduce the double-frequency ripple of the direct-current terminal voltage, so that the purpose of voltage stabilization control is achieved.

The application discloses an active front-end rectifier and a prediction control method thereof, and the method comprises the following steps: according to a voltage model of a three-level active front-end rectifier, calculating active power and reactive power of a power grid according to instantaneous power theory; according to the voltage model, combining the active power and the reactive power, calculating a power gradient; converting the power gradient into a second-order state space equation, predicting the control input of the active front-end rectifier by using a super-helix observer, and obtaining the input voltage of the active front-end rectifier according to the predicted control input and the grid-side voltage; based on the input voltage, obtaining an optimal voltage vector by using a limited set model prediction control framework, and controlling the active front-end rectifier based on the switching state corresponding to the optimal voltage vector. The method combines power gradient modeling, super-helix observer disturbance compensation and limited set prediction control, so that the rectifier overcomes the influence of parameter mismatch, and realizes high-sinusoidal current, stable DC voltage and power tracking control.

This invention discloses a simplified power point tracking (PPT) control method for NPC rectifiers, comprising: calculating the grid-side complex power S and the differential expression of the negative conjugate complex power based on the mathematical model of the three-level NPC rectifier and instantaneous power theory; discretizing the negative conjugate complex power at time k+1 in the dq rotating coordinate system using the forward Euler method; calculating the power error of the negative conjugate complex power under zero vector action at time k+1; performing preliminary vector pre-selection based on the sector where the power error is located; reducing the number of pre-selected vectors in each group in step four to four; cyclically calculating the predicted active and reactive power values ​​and the cost function J at time k+1, and determining the optimal vector. This invention simplifies the computational workload in the vector selection process of a three-level midpoint clamp rectifier by reducing polling pre-selection vectors, and introduces power point tracking error correction on the basis of traditional PI, thereby achieving accurate power point tracking control.

The invention relates to a cascade H-bridge energy storage device control method under a non-ideal power grid working condition. The method comprises the following steps of: firstly, performing positive and negative sequence decomposition on power grid voltage by adopting DSOGI-PLL to obtain frequency and phase information of a positive sequence component; then, calculating a grid-connected current reference value under the three-phase static coordinate system according to an instantaneous power theory and Park inverse transformation; the current controller adopts dead-beat prediction control, in order to eliminate control delay in digital control, a Luenberger observer is used for predicting grid-connected current at the moment K + 1, and then a Lagrange interpolation method is used for predicting power grid voltage at the moment K + 1 and a current reference value at the moment K + 2; and finally, calculating the number of input modules at the K + 1 moment through dead-beat prediction control, and generating a switching signal according to the number of input modules through nearest level modulation. According to the invention, the negative-sequence component and the harmonic component in the grid-connected current can be suppressed under the non-ideal power grid condition, the quality of the grid-connected electric energy is improved, and the cascaded H-bridge energy storage device has the operation capability under the non-ideal power grid condition.

The application discloses a renewable energy grid-connected system sub / super-synchronous collaborative suppression method, a terminal device and a storage medium, which are based on instantaneous power theory, sliding window fast Fourier transform, virtual resistance, phase compensation and the like. While effectively controlling the grid-side reactive power and the capacitor voltage of the sub-module, the sub / super-synchronous oscillation suppression current reference value is obtained through accurate extraction and conversion, so that the system can accurately suppress the oscillation. Different from the prior art, the virtual resistance value of the application does not need to be changed in the sub / super-synchronous oscillation frequency band; at the same time, the SWFFT algorithm is adopted for frequency locking adaptive control, so that the jumping and mixed oscillation frequencies can be identified at the same time; the collaborative suppression method is proposed for the problems of the symmetric amplification phenomenon in the single frequency sub / super-synchronous oscillation suppression and the inaccuracy of individual super-synchronous oscillation suppression, so that the problems are effectively solved and the stability of the system is improved.

The present invention discloses a method and system for controlling VSG current balance under voltage imbalance conditions. The method relates to the fields of power electronics and power system application technology. The method includes current balance control as the core of overall control, establishes a VSG model, analyzes the VSG output under unbalanced grid conditions, controls the VSG through active-frequency and reactive-voltage droop control, and then analyzes the VSG's instantaneous output power based on instantaneous power theory. When an unbalanced grid fault occurs, the positive and negative sequence currents are decomposed. By controlling the positive and negative sequence currents and incorporating voltage correction, current balance and power stability are achieved. The present invention designs current and power quality control for the VSG, achieving output current balance and maintaining active or reactive power without changing the VSG's characteristics.

The present application relates to the imbalance working condition based on the smooth switching of direct drive fan fault ride through control strategy, including the following steps, the mathematical model of the grid side inverter under the imbalance working condition is established, and the power expression of the grid side inverter under the imbalance working condition is given based on instantaneous power theory.Based on the established mathematical model and the given power expression, the smooth switching control strategy is designed and realized, so that the double common frequency oscillation of the active power output by the grid side converter and the grid current imbalance degree are reduced at the same time.The present application can well inhibit the double common frequency oscillation of the active power output by the grid side converter of direct drive wind turbine under the imbalance working condition and greatly reduce the grid current imbalance degree, so as to stabilize the DC side voltage during asymmetric fault and meet the grid current requirement.

A method for observing instantaneous power in a dual three-phase permanent magnet synchronous motor system relates to the field of motor control technology. The present invention addresses the difficulty of using traditional instantaneous power theory to observe power when the motor experiences asymmetric operation or fault conditions. The present invention performs vector space decoupling transformation and rotating coordinate transformation on the phase currents of the dual three-phase permanent magnet synchronous motor system. The difference between the obtained feedback currents in the dq plane and the z1z2 plane and the command currents of their corresponding axes is input into a current regulator to obtain the command voltages in the dq plane and the z1z2 plane. Spatial delay compensation is then performed to obtain the compensated voltage value. Based on the compensated voltage value and the feedback currents in the two planes, the instantaneous active power, instantaneous reactive power, instantaneous apparent power, and the instantaneous reactive power flow between each two axes of the dual three-phase permanent magnet synchronous motor system are calculated using a quaternion instantaneous power calculation formula.

The invention belongs to the field of network construction control, and discloses a cascade angle type static synchronous phase modulation network construction control method and system, and the method comprises the steps: calculating three-phase total active power and reactive power through employing an instantaneous power theory based on collected three-phase commutation chain angle external current and grid-connected point voltage; deriving a virtual internal potential frequency by using an active power difference value, and deriving a virtual internal potential reactive voltage regulation quantity amplitude by using a reactive power difference value; a three-phase virtual internal potential voltage amplitude is calculated through sine function summation; performing proportional-integral control on the difference value between the virtual internal potential frequency and the actual frequency of the power grid, and superposing a frequency feed-forward quantity to compensate a virtual internal potential phase angle; calculating a three-phase commutation chain current instruction based on a virtual impedance mechanism; and performing quasi-proportional resonance (PR) control on the current instruction and the in-angle current deviation to generate a modulation voltage, thereby realizing network construction control. By adopting the method, the complexity of traditional network construction control and current limiting is remarkably reduced, and stable and quick reactive voltage support, inertia and damping control can be realized without additional hardware.

The invention discloses an active front-end rectifier and a prediction control method thereof, and the method comprises the steps: calculating the active power and reactive power of a power grid according to a voltage model of a three-level active front-end rectifier and an instantaneous power theory; according to the voltage model, combining the active power and the reactive power to calculate a power gradient; converting the power gradient into a second-order state-space equation, predicting the control input of the active front-end rectifier by using a super-spiral observer, and obtaining the input voltage of the active front-end rectifier according to the predicted control input and the grid-side voltage; and based on the input voltage, obtaining an optimal voltage vector by adopting a finite set model predictive control framework, and controlling the active front-end rectifier based on the switching state corresponding to the optimal voltage vector. According to the method, power gradient modeling, superhelix observer disturbance compensation and finite set prediction control are combined, so that the rectifier overcomes the influence of parameter mismatch, and high-sine-degree current, stable direct-current voltage and power tracking control are realized.

The application discloses a kind of energy storage isolation type DC-DC resonant converter direct current suppression method and system, to optimize resonant network voltage ripple.The application constructs the voltage ripple mathematical model of resonant network using instantaneous power theory, by calculating the instantaneous power of resonant inductance and capacitance, and monitors the switching frequency of resonant converter is equal to the resonant frequency, is located in the resonant frequency and is away from the resonant frequency three kinds of working conditions, when in corresponding condition, according to corresponding method to determine the range limit of switching frequency, based on this, the switching frequency of resonant converter is dynamically adjusted with different working conditions, to effectively suppress output DC ripple, improve the reliability of power quality guarantee system.