The invention discloses a power signal frequency detection method and a power signal frequency detection system based on phase modulation. The method comprises the steps: sampling a power signal according to preset signal time span and preset sampling frequency, so as to obtain an input signal sequence; measuring the frequency of the input signal sequence, so as to obtain the initial frequency of the power signal, and subtracting the input signal sequence and the plus or minus 1 Pi phase-shift sequence of the input signal sequence by using the initial frequency as reference frequency, so as to obtain two phase modulation sequences of which phases change along with the input signal frequency; respectively mixing, filtering and integrating the two phase modulation sequences, so as to obtain the phases of the two phase modulation phases for frequency measurement. By implementing the power signal frequency detection method and the power signal frequency detection system, frequency measurement results with higher accuracy can be obtained.

Power signal frequency detection method and system based on amplitude modulation

The invention discloses a sinusoidal parameter measurement method and system of a power signal. The method comprises the following steps: performing preliminary measurement on fundamental wave frequency of a sampling data sequence to acquire preliminary fundamental wave frequency and multiplying a cosine function and a sine function of the preliminary fundamental wave frequency serving as the reference frequency by the sampling data sequence respectively to generate a real vector sequence and an imaginary vector sequence; performing digital filtering on the real vector sequence and the imaginary vector sequence to generate a real vector filter sequence and an imaginary vector filter sequence, and further integrating to generate a real vector integral value and an imaginary vector integral value; converting the real vector integral value and the imaginary vector integral value into corresponding sinusoidal parameters according to a preset sinusoidal parameter conversion rule. By implementing the method and the system, mixed frequency interference elements in the real vector sequence and the imaginary vector sequence can be inhibited to generate high-precision real vector and imaginary vector sequence integral values so as to finally obtain the sinusoidal parameters with higher precision.

Sinusoidal parameter measurement method and system of power signal

The invention discloses a voltage regulation method based on inverter power coordination control. The method comprises the steps that during one sampling period, a constrained and optimized mathematical model is used for conducting power coordination control over photovoltaic inverters; the objective function (shown in the specification) of the constrained and optimized mathematical model is the minimum of the sum of reactive power output by all photovoltaic power sources, and the constraint conditions include the inverter capacity constraint, the node flow constraint, the node voltage constraint and the inverter power adjustment weight constraint; on the condition of meeting all the proposed constraint conditions, a set of reactive power adjustment quantities of the minimum sum of the reactive power output by all the photovoltaic power sources are solved through an optimization algorithm and serve as reactive power reference values for coordination control over all the photovoltaic inverters, and voltage adjustment of grid-connection points in an area is achieved. By means of the method, on the premise of not reducing the photovoltaic output active power, the voltage adjustment capacity of each inverter can be fully utilized, and the situation that unnecessary lien power losses are caused by output of excessive reactive power can be avoided.

Voltage regulation method based on inverter power coordination control

The invention discloses a power grid voltage phase lock method for zero voltage ride through of a photovoltaic grid-connected inverter, and discloses a zero voltage ride through control method for the photovoltaic grid-connected inverter The method comprises a power grid voltage phase lock method, an active current control method and a reactive current control method in a zero voltage ride through process of the photovoltaic grid-connected inverter The phase lock method is used for supplying a phase to current control in the zero voltage ride through process According to the power grid voltage phase lock method disclosed by the invention, the inverter can perform automatic amplitude limitation on active current conveyed to a power grid in a power grid voltage falling process and also quickly recover the amplitude after the power grid voltage is recovered; meanwhile, the inverter has the capability of sending reactive current to the power grid according to the reduction degree of the amplitude of the power grid voltage

Power grid voltage phase lock method for zero voltage ride through of photovoltaic grid-connected inverter

The invention relates to a distributed energy grid connection and reactive compensation composite control method, which comprises the following processes of obtaining real-time grid voltage VS, system current IS and DC bus voltage Vdc through a collection module and then transmitting the real-time grid voltage VS, the system current IS and the DC bus voltage Vdc to a digital signal processor DSP; and obtaining reactive current and grid-connected current in a load through calculation, comparing the reactive current and the grid-connected current with a set adjustment target value, generating a fixed-frequency PWM pulse through a PI controller to drive an inverter power tube IGBT to be turned on and turned off, controlling output of each phase of grid-connected current and compensation current of a system, and outputting the maximum grid-connected power by the system in an active priority mode, firstly compensating the reactive current of the system in a regional reactive priority mode and providing the system with active compensation and reactive compensation in a regional balance mode. Through controlling output of each phase of grid-connected current and compensation current of the system, a distributed energy access device can be more intelligently used for a regional power grid and has the characteristic of high grid-connection efficiency.

Distributed energy grid connection and reactive compensation composite control method

The invention discloses a reactive voltage control method and system for a grid-connected photovoltaic power station. A three-layer reactive power control strategy is adopted to coordinate the reactive output between a reactive compensation device and a photovoltaic power generation unit and between inverters of a single photovoltaic power generation unit. Under the control strategy, the reactive voltage support is provided for the power grid; the photovoltaic power station can effectively regulate the power grid voltage; the active loss and the reactive loss of the power grid are minimal on the premise of keeping the power grid voltage within the required range. A photovoltaic array power reduction running strategy is further combined, the stable operation of the power grid is ensured on the premise of maintaining a certain reactive output capacity of the photovoltaic power station. The reactive voltage control method and the system solve the problem that the voltage at the grid-connected point is out of limit, which is caused by the fact that the large-scale photovoltaic power station is connected to the power grid, increase the permeability of the photovoltaic current in the power grid, and improve the stable running performance of the power grid voltage.

Reactive voltage control method and system for grid-connected photovoltaic power station

The invention discloses a photovoltaic grid connected direct current injecting restraining method. The photovoltaic grid connected direct current injecting restraining method adopts the control strategy that dual controllers of PR plus PI or quasi-PR plus PI are used as a grid connected electric current loop controller, restraining is conducted on direct current injecting caused by inconformity of movements of inverter bridge switching devices through feedback control. Under the condition that detecting circuits are not additionally arranged, the PR controller or the quasi-PR controller is used as the grid connected electric current loop controller, alternating current controlled signals in assigned frequency can be controlled in a stable-state and difference-free mode in a stationary coordinate system, an unity-power-factor grid connected mode is achieved, and the PI controller is used for effectively restraining direct current amount.

Photovoltaic grid connected direct current injecting restraining method

The invention discloses a power grid synchronous signal real-time detection method and system based on reference frequency, and relates to the field of voltage synchronous signal detection. According to the method, negative feedback and proportional control are introduced into a low-pass filtering link in the detection process so that satisfying indexes of correction of phase deviation can be obtained. The problem that due to frequency deviation of a power grid, large phase deviation occurs to a detected synchronous signal is solved. Single-phase power grid voltage and sine and cosine signal operations of reference frequency are detected only, and even if under the condition that a three-phase power grid distorts and is unbalanced, the power grid synchronous signal can be accurately detected. The invention further discloses a power grid synchronous signal real-time detection system based on the reference frequency. According to the system, negative feedback and proportional control enable phase deviation to be obviously corrected, according to a deducted expression of phase deviation and a proportional control coefficient K, a value is obtained, a satisfying result can be obtained, and as is proved, the power grid synchronous signal real-time detection system has correctness and validness.

Zheng Guanghui

Papers

Reactive voltage control method and system for grid-connected photovoltaic power station

Photovoltaic grid connected direct current injecting restraining method

Power grid synchronous signal real-time detection method and system based on reference frequency